diff --git a/gtk2_ardour/editor.cc b/gtk2_ardour/editor.cc
index 4e33e25aef..ead62ea4e7 100644
--- a/gtk2_ardour/editor.cc
+++ b/gtk2_ardour/editor.cc
@@ -229,7 +229,7 @@ static const gchar *_rb_opt_strings[] = {
 #endif
 
 Editor::Editor ()
-	: PublicEditor (global_hpacker)
+	: PublicEditor ()
 	, editor_mixer_strip_width (Wide)
 	, constructed (false)
 	, _properties_box (0)
@@ -660,23 +660,13 @@ Editor::Editor ()
 	_summary_hbox.pack_start (*summary_arrows_right, false, false);
 
 	editor_summary_pane.add (_summary_hbox);
-	edit_pane.set_check_divider_position (true);
-	edit_pane.add (editor_summary_pane);
 	_editor_list_vbox.pack_start (_the_notebook);
 	_editor_list_vbox.pack_start (*_properties_box, false, false, 0);
-	edit_pane.add (_editor_list_vbox);
-	edit_pane.set_child_minsize (_editor_list_vbox, 30); /* rough guess at width of notebook tabs */
 
-	edit_pane.set_drag_cursor (*_cursors->expand_left_right);
+	content_right_pane.set_drag_cursor (*_cursors->expand_left_right);
 	editor_summary_pane.set_drag_cursor (*_cursors->expand_up_down);
 
 	float fract;
-	if (!settings || !settings->get_property ("edit-horizontal-pane-pos", fract) || fract > 1.0) {
-		/* initial allocation is 90% to canvas, 10% to notebook */
-		fract = 0.90;
-	}
-	edit_pane.set_divider (0, fract);
-
 	if (!settings || !settings->get_property ("edit-vertical-pane-pos", fract) || fract > 1.0) {
 		/* initial allocation is 90% to canvas, 10% to summary */
 		fract = 0.90;
@@ -686,20 +676,6 @@ Editor::Editor ()
 	global_vpacker.set_spacing (0);
 	global_vpacker.set_border_width (0);
 
-	/* the next three EventBoxes provide the ability for their child widgets to have a background color.  That is all. */
-
-	Gtk::EventBox* ebox = manage (new Gtk::EventBox); // a themeable box
-	ebox->set_name("EditorWindow");
-	ebox->add (ebox_hpacker);
-
-	Gtk::EventBox* epane_box = manage (new EventBoxExt); // a themeable box
-	epane_box->set_name("EditorWindow");
-	epane_box->add (edit_pane);
-
-	Gtk::EventBox* epane_box2 = manage (new EventBoxExt); // a themeable box
-	epane_box2->set_name("EditorWindow");
-	epane_box2->add (global_vpacker);
-
 	ArdourWidgets::ArdourDropShadow *toolbar_shadow = manage (new (ArdourWidgets::ArdourDropShadow));
 	toolbar_shadow->set_size_request (-1, 4);
 	toolbar_shadow->set_mode(ArdourWidgets::ArdourDropShadow::DropShadowBoth);
@@ -707,16 +683,21 @@ Editor::Editor ()
 	toolbar_shadow->show();
 
 	global_vpacker.pack_start (*toolbar_shadow, false, false);
-	global_vpacker.pack_start (*ebox, false, false);
-	global_vpacker.pack_start (*epane_box, true, true);
-	global_hpacker.pack_start (*epane_box2, true, true);
+	global_vpacker.pack_start (editor_summary_pane, true, true);
+
+	/* pack all the main pieces into appropriate containers from _tabbable
+	 */
+	content_app_bar.add (_application_bar);
+	content_att_right.add (_editor_list_vbox);
+	content_toolbar.add (ebox_hpacker);
+	content_innermost_hbox.add (global_vpacker);
 
 	/* need to show the "contents" widget so that notebook will show if tab is switched to
 	 */
 
-	global_hpacker.show ();
+	content_hbox.show ();
 	ebox_hpacker.show();
-	ebox->show();
+	global_vpacker.show();
 
 	/* register actions now so that set_state() can find them and set toggles/checks etc */
 
@@ -2329,7 +2310,6 @@ Editor::get_state () const
 
 	node->add_child_nocopy (Tabbable::get_state());
 
-	node->set_property("edit-horizontal-pane-pos", edit_pane.get_divider ());
 	node->set_property("notebook-shrunk", _notebook_shrunk);
 	node->set_property("edit-vertical-pane-pos", editor_summary_pane.get_divider());
 
@@ -5511,7 +5491,7 @@ Editor::session_going_away ()
 
 	if (current_mixer_strip) {
 		if (current_mixer_strip->get_parent() != 0) {
-			global_hpacker.remove (*current_mixer_strip);
+			content_att_left.remove ();
 		}
 		delete current_mixer_strip;
 		current_mixer_strip = 0;
@@ -5660,16 +5640,16 @@ Editor::notebook_tab_clicked (GdkEventButton* ev, Gtk::Widget* page)
 
 		if (_notebook_shrunk) {
 			if (pre_notebook_shrink_pane_width) {
-				edit_pane.set_divider (0, *pre_notebook_shrink_pane_width);
+				content_right_pane.set_divider (0, *pre_notebook_shrink_pane_width);
 			}
 			_notebook_shrunk = false;
 		} else {
-			pre_notebook_shrink_pane_width = edit_pane.get_divider();
+			pre_notebook_shrink_pane_width = content_right_pane.get_divider();
 
 			/* this expands the LHS of the edit pane to cover the notebook
 			   PAGE but leaves the tabs visible.
 			 */
-			edit_pane.set_divider (0, edit_pane.get_divider() + page->get_width());
+			content_right_pane.set_divider (0, content_right_pane.get_divider() + page->get_width());
 			_notebook_shrunk = true;
 		}
 	}
@@ -5709,7 +5689,7 @@ Editor::ui_parameter_changed (string parameter)
 		}
 		_cursors->set_cursor_set (UIConfiguration::instance().get_icon_set());
 		_cursor_stack.push_back(_cursors->grabber);
-		edit_pane.set_drag_cursor (*_cursors->expand_left_right);
+		content_right_pane.set_drag_cursor (*PublicEditor::instance().cursors()->expand_left_right);
 		editor_summary_pane.set_drag_cursor (*_cursors->expand_up_down);
 
 	} else if (parameter == "sensitize-playhead") {
diff --git a/gtk2_ardour/editor.h b/gtk2_ardour/editor.h
index f665ffb46f..66054268c1 100644
--- a/gtk2_ardour/editor.h
+++ b/gtk2_ardour/editor.h
@@ -589,7 +589,6 @@ private:
 	void add_notebook_page (std::string const&, Gtk::Widget&);
 	bool notebook_tab_clicked (GdkEventButton*, Gtk::Widget*);
 
-	ArdourWidgets::HPane edit_pane;
 	ArdourWidgets::VPane editor_summary_pane;
 
 	Gtk::EventBox meter_base;
@@ -766,7 +765,6 @@ private:
 	void timeaxisview_deleted (TimeAxisView*);
 	void add_vcas (ARDOUR::VCAList&);
 
-	Gtk::HBox global_hpacker;
 	Gtk::VBox global_vpacker;
 
 	Gdk::Cursor* which_track_cursor () const;
diff --git a/gtk2_ardour/editor_actions.cc b/gtk2_ardour/editor_actions.cc
index 87c63f81e1..04b02b220b 100644
--- a/gtk2_ardour/editor_actions.cc
+++ b/gtk2_ardour/editor_actions.cc
@@ -754,7 +754,7 @@ void
 Editor::load_bindings ()
 {
 	bindings = Bindings::get_bindings (editor_name());
-	global_hpacker.set_data ("ardour-bindings", bindings);
+	contents().set_data ("ardour-bindings", bindings);
 
 	/* This set of bindings may expand in the future to include things
 	 * other than MIDI editing, but for now this is all we've got as far as
diff --git a/gtk2_ardour/editor_mixer.cc b/gtk2_ardour/editor_mixer.cc
index 4f5ed4cf81..dc47d4f2fc 100644
--- a/gtk2_ardour/editor_mixer.cc
+++ b/gtk2_ardour/editor_mixer.cc
@@ -151,8 +151,8 @@ Editor::show_editor_mixer (bool yn)
 		}
 
 		if (current_mixer_strip && current_mixer_strip->get_parent() == 0) {
-			global_hpacker.pack_start (*current_mixer_strip, Gtk::PACK_SHRINK );
-			global_hpacker.reorder_child (*current_mixer_strip, 0);
+			content_hbox.pack_start (*current_mixer_strip, Gtk::PACK_SHRINK );
+			content_hbox.reorder_child (*current_mixer_strip, 0);
 			current_mixer_strip->show ();
 		}
 
@@ -165,7 +165,7 @@ Editor::show_editor_mixer (bool yn)
 
 		if (current_mixer_strip) {
 			if (current_mixer_strip->get_parent() != 0) {
-				global_hpacker.remove (*current_mixer_strip);
+				content_hbox.remove (*current_mixer_strip);
 			}
 		}
 	}
diff --git a/gtk2_ardour/mixer_ui.cc b/gtk2_ardour/mixer_ui.cc
index 2630f68d59..337793c031 100644
--- a/gtk2_ardour/mixer_ui.cc
+++ b/gtk2_ardour/mixer_ui.cc
@@ -55,6 +55,7 @@
 #include "ardour/monitor_control.h"
 #include "ardour/panner_shell.h"
 #include "ardour/plugin_manager.h"
+#include "ardour/profile.h"
 #include "ardour/route_group.h"
 #include "ardour/selection.h"
 #include "ardour/session.h"
@@ -132,7 +133,7 @@ Mixer_UI::instance ()
 }
 
 Mixer_UI::Mixer_UI ()
-	: Tabbable (_("Mixer"), X_("mixer"), &_content)
+	: Tabbable (_("Mixer"), X_("mixer"))
 	, plugin_search_clear_button (X_("Clear"))
 	, _mixer_scene_release (0)
 	, no_track_list_redisplay (false)
@@ -161,7 +162,7 @@ Mixer_UI::Mixer_UI ()
 	Glib::RefPtr<ToggleAction> fb_act = ActionManager::get_toggle_action ("Mixer", "ToggleFoldbackStrip");
 	fb_act->set_sensitive (false);
 
-	_content.set_data ("ardour-bindings", bindings);
+	contents().set_data ("ardour-bindings", bindings);
 
 	PresentationInfo::Change.connect (*this, invalidator (*this), std::bind (&Mixer_UI::presentation_info_changed, this, _1), gui_context());
 	Route::FanOut.connect (*this, invalidator (*this), std::bind (&Mixer_UI::fan_out, this, _1, false, true), gui_context());
@@ -375,27 +376,26 @@ Mixer_UI::Mixer_UI ()
 	global_hpacker.pack_start (inner_pane, true, true);
 	global_hpacker.pack_start (out_packer, false, false);
 
-	list_hpane.set_check_divider_position (true);
-	list_hpane.add (list_vpacker);
-	list_hpane.add (global_hpacker);
-	list_hpane.set_child_minsize (list_vpacker, 30);
-
 	rhs_pane1.set_divider (0, .6);
 	rhs_pane2.set_divider (0, .7);
-	list_hpane.set_divider (0, .2);
 	inner_pane.set_divider (0, .8);
 
 	rhs_pane1.set_drag_cursor (*PublicEditor::instance().cursors()->expand_up_down);
 	rhs_pane2.set_drag_cursor (*PublicEditor::instance().cursors()->expand_up_down);
-	list_hpane.set_drag_cursor (*PublicEditor::instance().cursors()->expand_left_right);
 	inner_pane.set_drag_cursor (*PublicEditor::instance().cursors()->expand_left_right);
 
-	_content.pack_start (list_hpane, true, true);
+	content_app_bar.add (_application_bar);
+	content_innermost_hbox.add (global_hpacker);
+
+	if (!Profile->get_mixbus ()) {
+		content_att_left.add (list_vpacker);
+	} else {
+		content_att_right.add (list_vpacker);
+	}
 
 	update_title ();
 
-	_content.show ();
-	_content.set_name ("MixerWindow");
+	contents().set_name ("MixerWindow");
 
 	global_hpacker.show();
 	scroller.show();
@@ -420,7 +420,6 @@ Mixer_UI::Mixer_UI ()
 	vca_label.show();
 	vca_scroller_base.show();
 	out_packer.show();
-	list_hpane.show();
 	group_display.show();
 	favorite_plugins_display.show();
 
@@ -1483,7 +1482,7 @@ Mixer_UI::stop_updating ()
 void
 Mixer_UI::fast_update_strips ()
 {
-	if (!UIConfiguration::instance().get_no_strobe() && _content.get_mapped () && _session) {
+	if (!UIConfiguration::instance().get_no_strobe() && contents().get_mapped () && _session) {
 		for (auto & s : strips) {
 			s->fast_update ();
 		}
@@ -2648,11 +2647,6 @@ Mixer_UI::set_state (const XMLNode& node, int version)
 	}
 	rhs_pane2.set_divider (0, fract);
 
-	if (!node.get_property ("mixer-list-hpane-pos", fract) || fract > 1.0) {
-		fract = 0.2f;
-	}
-	list_hpane.set_divider (0, fract);
-
 	if (!node.get_property ("mixer-inner-pane-pos", fract) || fract > 1.0) {
 		fract = 0.8f;
 	}
@@ -2699,7 +2693,6 @@ Mixer_UI::get_state () const
 
 	node->set_property (X_("mixer-rhs-pane1-pos"), rhs_pane1.get_divider());
 	node->set_property (X_("mixer-rhs_pane2-pos"), rhs_pane2.get_divider());
-	node->set_property (X_("mixer-list-hpane-pos"), list_hpane.get_divider());
 	node->set_property (X_("mixer-inner-pane-pos"),  inner_pane.get_divider());
 
 	node->set_property ("narrow-strips", (_strip_width == Narrow));
@@ -3024,7 +3017,7 @@ Mixer_UI::strip_by_x (int x)
 	for (list<MixerStrip*>::iterator i = strips.begin(); i != strips.end(); ++i) {
 		int x1, x2, y;
 
-		(*i)->translate_coordinates (_content, 0, 0, x1, y);
+		(*i)->translate_coordinates (contents(), 0, 0, x1, y);
 		x2 = x1 + (*i)->get_width();
 
 		if (x >= x1 && x <= x2) {
diff --git a/gtk2_ardour/mixer_ui.h b/gtk2_ardour/mixer_ui.h
index fe1042c56e..9e760aa68f 100644
--- a/gtk2_ardour/mixer_ui.h
+++ b/gtk2_ardour/mixer_ui.h
@@ -177,7 +177,7 @@ protected:
 private:
 	Mixer_UI ();
 	static Mixer_UI*     _instance;
-	Gtk::VBox            _content;
+
 	Gtk::HBox             global_hpacker;
 	Gtk::VBox             global_vpacker;
 	Gtk::ScrolledWindow   scroller;
@@ -210,7 +210,6 @@ private:
 	Gtk::Label            vca_label;
 	Gtk::EventBox         vca_scroller_base;
 	Gtk::HBox             out_packer;
-	ArdourWidgets::HPane  list_hpane;
 
 	Gtk::EventBox         _mixer_scene_spacer;
 	Gtk::Frame            _mixer_scene_frame;
diff --git a/gtk2_ardour/public_editor.cc b/gtk2_ardour/public_editor.cc
index 7efad6055a..5531424582 100644
--- a/gtk2_ardour/public_editor.cc
+++ b/gtk2_ardour/public_editor.cc
@@ -31,9 +31,9 @@ const int PublicEditor::horizontal_spacing = 6;
 
 ARDOUR::DataType PublicEditor::pbdid_dragged_dt = ARDOUR::DataType::NIL;
 
-PublicEditor::PublicEditor (Gtk::Widget& content)
+PublicEditor::PublicEditor ()
 	: EditingContext (X_("Editor"))
-	, Tabbable (_("Editor"), X_("editor"), &content)
+	, Tabbable (_("Editor"), X_("editor"))
 {
 	_suspend_route_redisplay_counter.store (0);
 }
diff --git a/gtk2_ardour/public_editor.h b/gtk2_ardour/public_editor.h
index 1225db9448..b2339bfaf3 100644
--- a/gtk2_ardour/public_editor.h
+++ b/gtk2_ardour/public_editor.h
@@ -126,7 +126,7 @@ using ARDOUR::samplecnt_t;
 class PublicEditor : public EditingContext, public ArdourWidgets::Tabbable
 {
 public:
-	PublicEditor (Gtk::Widget& content);
+	PublicEditor ();
 	virtual ~PublicEditor ();
 
 	/** @return Singleton PublicEditor instance */
diff --git a/gtk2_ardour/recorder_ui.cc b/gtk2_ardour/recorder_ui.cc
index 7d5f3d2021..2ee4edbde8 100644
--- a/gtk2_ardour/recorder_ui.cc
+++ b/gtk2_ardour/recorder_ui.cc
@@ -78,7 +78,7 @@ using namespace Menu_Helpers;
 #define PX_SCALE(px) std::max ((float)px, rintf ((float)px* UIConfiguration::instance ().get_ui_scale ()))
 
 RecorderUI::RecorderUI ()
-	: Tabbable (_("Recorder"), X_("recorder"), &_content)
+	: Tabbable (_("Recorder"), X_("recorder"))
 	, _toolbar_sep (1.0)
 	, _btn_rec_all (_("All"))
 	, _btn_rec_none (_("None"))
@@ -193,9 +193,10 @@ RecorderUI::RecorderUI ()
 	_pane.add (_meter_scroller);
 
 	/* Top-level VBox */
-	_content.pack_start (_toolbar_sep, false, false, 1);
-	_content.pack_start (_toolbar, false, false, 2);
-	_content.pack_start (_pane, true, true);
+	content_app_bar.add (_application_bar);
+	//content_att_right.add (_editor_list_vbox); // TODO
+	content_toolbar.add(_toolbar);
+	content_innermost_hbox.add (_pane);
 
 	/* button_table setup is similar to transport_table in ardour_ui */
 	int vpadding = 1;
@@ -280,10 +281,9 @@ RecorderUI::RecorderUI ()
 	_meter_area.show ();
 	_meter_scroller.show ();
 	_pane.show ();
-	_content.show ();
 
 	/* setup keybidings */
-	_content.set_data ("ardour-bindings", bindings);
+	contents().set_data ("ardour-bindings", bindings);
 
 	/* subscribe to signals */
 	AudioEngine::instance ()->Running.connect (_engine_connections, invalidator (*this), std::bind (&RecorderUI::start_updating, this), gui_context ());
diff --git a/gtk2_ardour/recorder_ui.h b/gtk2_ardour/recorder_ui.h
index a466ff2376..38ddaad132 100644
--- a/gtk2_ardour/recorder_ui.h
+++ b/gtk2_ardour/recorder_ui.h
@@ -126,7 +126,6 @@ private:
 	static int calc_columns (int child_width, int parent_width);
 
 	Gtkmm2ext::Bindings*  bindings;
-	Gtk::VBox            _content;
 	Gtk::HBox            _toolbar;
 	Gtk::Table           _button_table;
 	ArdourWidgets::VPane _pane;
diff --git a/gtk2_ardour/trigger_page.cc b/gtk2_ardour/trigger_page.cc
index 03e9826579..1558f16a12 100644
--- a/gtk2_ardour/trigger_page.cc
+++ b/gtk2_ardour/trigger_page.cc
@@ -66,11 +66,12 @@ using namespace Gtk;
 using namespace std;
 
 TriggerPage::TriggerPage ()
-	: Tabbable (_("Cues"), X_("trigger"), &_content)
+	: Tabbable (_("Cues"), X_("trigger"))
 	, _cue_area_frame (0.5, 0, 1.0, 0)
 	, _cue_box (16, 16 * TriggerBox::default_triggers_per_box)
 	, _master_widget (16, 16)
 	, _master (_master_widget.root ())
+	, _show_bottom_pane (false)
 	, _selection (*this, *this)
 {
 	load_bindings ();
@@ -126,16 +127,11 @@ TriggerPage::TriggerPage ()
 	_sidebar_notebook.popup_disable ();
 	_sidebar_notebook.set_tab_pos (Gtk::POS_RIGHT);
 
-	_sidebar_vbox.pack_start (_sidebar_notebook);
 	add_sidebar_page (_("Clips"), _trigger_clip_picker);
 	add_sidebar_page (_("Tracks"), _trigger_route_list.widget ());
 	add_sidebar_page (_("Sources"), _trigger_source_list.widget ());
 	add_sidebar_page (_("Regions"), _trigger_region_list.widget ());
 
-	/* Upper pane ([slot | strips] | file browser) */
-	_pane_upper.add (_strip_group_box);
-	_pane_upper.add (_sidebar_vbox);
-
 	_midi_editor = new MidiCueEditor;
 
 	/* Bottom -- Properties of selected Slot/Region */
@@ -152,15 +148,25 @@ TriggerPage::TriggerPage ()
 	table->attach (_midi_editor->toolbox(), col, col + 1, 0, 1, Gtk::EXPAND|Gtk::FILL, Gtk::EXPAND|Gtk::FILL);
 	++col;
 
+	table->show_all ();
+
 	_parameter_box.pack_start (*table);
+	_parameter_box.set_no_show_all ();
 
 	/* Top-level Layout */
-	_content.add (_pane_upper);
-	_content.add (_parameter_box);
-	_content.show ();
+	content_app_bar.add (_application_bar);
+	content_innermost_hbox.add (_pane);
+
+	_pane.add (_strip_group_box);
+	/* we cannot `content_midlevel_vbox.remove(_content_att_bottom)` and add it to the _pane
+	 * because visibility updates are not propagated upward, and the pane will not collapse
+	 * when the _parameter_box is hidden
+	 */
+	_pane.add (_parameter_box);
+
+	content_att_right.add (_sidebar_notebook);
 
 	/* Show all */
-	_pane_upper.show ();
 	_strip_group_box.show ();
 	_strip_scroller.show ();
 	_strip_packer.show ();
@@ -170,7 +176,7 @@ TriggerPage::TriggerPage ()
 	_sidebar_notebook.show_all ();
 
 	/* setup keybidings */
-	_content.set_data ("ardour-bindings", bindings);
+	contents().set_data ("ardour-bindings", bindings);
 
 	/* subscribe to signals */
 	Config->ParameterChanged.connect (*this, invalidator (*this), std::bind (&TriggerPage::parameter_changed, this, _1), gui_context ());
@@ -178,14 +184,6 @@ TriggerPage::TriggerPage ()
 
 	/* init */
 	update_title ();
-
-	/* Restore pane state */
-	float          fract;
-	XMLNode const* settings = ARDOUR_UI::instance ()->trigger_page_settings ();
-	if (!settings || !settings->get_property ("triggerpage-hpane-pos", fract) || fract > 1.0) {
-		fract = 0.75f;
-	}
-	_pane_upper.set_divider (0, fract);
 }
 
 TriggerPage::~TriggerPage ()
@@ -216,13 +214,28 @@ TriggerPage::use_own_window (bool and_fill_it)
 	return win;
 }
 
+void
+TriggerPage::showhide_att_bottom (bool yn)
+{
+	if (_show_bottom_pane == yn) {
+		return;
+	}
+
+	_show_bottom_pane = yn;
+
+	if (!_show_bottom_pane) {
+		_parameter_box.hide ();
+	} else if (!Editor::instance ().get_selection ().triggers.empty ()) {
+		_parameter_box.show ();
+	}
+}
+
 XMLNode&
 TriggerPage::get_state () const
 {
 	XMLNode* node = new XMLNode (X_("TriggerPage"));
 	node->add_child_nocopy (Tabbable::get_state ());
 
-	node->set_property (X_("triggerpage-hpane-pos"), _pane_upper.get_divider ());
 	node->set_property (X_("triggerpage-sidebar-page"), _sidebar_notebook.get_current_page ());
 
 	node->add_child_nocopy (_midi_editor->get_state());
@@ -425,7 +438,9 @@ TriggerPage::rec_enable_changed (Trigger const * trigger)
 		_midi_editor->viewport().show ();
 	}
 
-	_parameter_box.show ();
+	if (_show_bottom_pane) {
+		_parameter_box.show ();
+	}
 }
 
 void
@@ -465,7 +480,9 @@ TriggerPage::selection_changed ()
 			_midi_editor->viewport().show ();
 		}
 
-		_parameter_box.show ();
+		if (_show_bottom_pane) {
+			_parameter_box.show ();
+		}
 	}
 }
 
@@ -817,7 +834,7 @@ TriggerPage::stop_updating ()
 void
 TriggerPage::fast_update_strips ()
 {
-	if (_content.get_mapped () && _session) {
+	if (contents().get_mapped () && _session) {
 		for (list<TriggerStrip*>::iterator i = _strips.begin (); i != _strips.end (); ++i) {
 			(*i)->fast_update ();
 		}
diff --git a/gtk2_ardour/trigger_page.h b/gtk2_ardour/trigger_page.h
index 210b33a91c..129d242e42 100644
--- a/gtk2_ardour/trigger_page.h
+++ b/gtk2_ardour/trigger_page.h
@@ -81,6 +81,8 @@ private:
 	void pi_property_changed (PBD::PropertyChange const&);
 	void stripable_property_changed (PBD::PropertyChange const&, std::weak_ptr<ARDOUR::Stripable>);
 
+	void showhide_att_bottom (bool);
+
 	void rec_state_changed ();
 	void rec_state_clicked ();
 
@@ -108,9 +110,8 @@ private:
 	ApplicationBar _application_bar;
 
 	Gtkmm2ext::Bindings* bindings;
-	ArdourWidgets::VPane _content;
 
-	ArdourWidgets::HPane _pane_upper;
+	ArdourWidgets::VPane _pane;
 	Gtk::HBox            _strip_group_box;
 	Gtk::ScrolledWindow  _strip_scroller;
 	Gtk::HBox            _strip_packer;
@@ -118,7 +119,6 @@ private:
 	Gtk::Alignment       _cue_area_frame;
 	Gtk::VBox            _cue_area_box;
 	Gtk::HBox            _parameter_box;
-	Gtk::VBox            _sidebar_vbox;
 	Gtk::Notebook        _sidebar_notebook;
 	TriggerClipPicker    _trigger_clip_picker;
 	TriggerSourceList    _trigger_source_list;
@@ -129,6 +129,8 @@ private:
 	FittedCanvasWidget _master_widget;
 	CueMaster          _master;
 
+	bool _show_bottom_pane;
+
 	SlotPropertiesBox _slot_prop_box;
 
 	AudioTriggerPropertiesBox _audio_trig_box;