diff --git a/gtk2_ardour/mixer_ui.cc b/gtk2_ardour/mixer_ui.cc
index dd581dbfb9..ac12d5a21f 100644
--- a/gtk2_ardour/mixer_ui.cc
+++ b/gtk2_ardour/mixer_ui.cc
@@ -133,7 +133,7 @@ Mixer_UI::instance ()
 }
 
 Mixer_UI::Mixer_UI ()
-	: Tabbable (_("Mixer"), X_("mixer"))
+	: Tabbable (_("Mixer"), X_("mixer"), NULL, true, Profile->get_mixbus () ? Tabbable::PaneRightBtm : Tabbable::PaneLeft)
 	, plugin_search_clear_button (X_("Clear"))
 	, _mixer_scene_release (0)
 	, no_track_list_redisplay (false)
@@ -164,13 +164,6 @@ Mixer_UI::Mixer_UI ()
 
 	contents().set_data ("ardour-bindings", bindings);
 
-	if (!Profile->get_mixbus ()) {
-		right_attachment_button.set_sensitive(false);
-	} else {
-		left_attachment_button.set_sensitive(false);
-	}
-	bottom_attachment_button.set_sensitive(false);
-
 	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());
 
@@ -415,7 +408,7 @@ Mixer_UI::Mixer_UI ()
 	favorite_plugins_scroller.show();
 	group_display_vbox.show();
 	group_display_frame.show();
-	favorite_plugins_frame.show();
+	favorite_plugins_frame.show_all();
 	rhs_pane1.show();
 	rhs_pane2.show();
 	strip_packer.show();
@@ -3717,7 +3710,6 @@ Mixer_UI::register_actions ()
 		act = ActionManager::register_toggle_action (group, "ToggleMixerList", _("(Mixer) Show Sidebar List"), sigc::mem_fun (*this, &Tabbable::att_left_button_toggled));
 		left_attachment_button.set_related_action (act);
 		act = ActionManager::register_toggle_action (group, "ToggleMixerStrip", _("(Mixer) Show Sidebar Strip"), []{});
-		content_right_pane.remove(content_right_vbox);
 	} else {
 		act = ActionManager::register_toggle_action (group, "ToggleMixerList", _("(Mixer) Show Sidebar List"), sigc::mem_fun (*this, &Tabbable::att_right_button_toggled));
 		right_attachment_button.set_related_action (act);
diff --git a/gtk2_ardour/public_editor.cc b/gtk2_ardour/public_editor.cc
index 5531424582..83f4b47e51 100644
--- a/gtk2_ardour/public_editor.cc
+++ b/gtk2_ardour/public_editor.cc
@@ -33,7 +33,7 @@ ARDOUR::DataType PublicEditor::pbdid_dragged_dt = ARDOUR::DataType::NIL;
 
 PublicEditor::PublicEditor ()
 	: EditingContext (X_("Editor"))
-	, Tabbable (_("Editor"), X_("editor"))
+	, Tabbable (_("Editor"), X_("editor"), NULL, true, Tabbable::PaneLayout (Tabbable::AttLeft | Tabbable::PaneRightBtm))
 {
 	_suspend_route_redisplay_counter.store (0);
 }
diff --git a/gtk2_ardour/recorder_ui.cc b/gtk2_ardour/recorder_ui.cc
index 1ad597958f..eea71a86e6 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"))
+	: Tabbable (_("Recorder"), X_("recorder"), NULL, true, Tabbable::NoPanes)
 	, _toolbar_sep (1.0)
 	, _btn_rec_all (_("All"))
 	, _btn_rec_none (_("None"))
@@ -101,11 +101,6 @@ RecorderUI::RecorderUI ()
 	load_bindings ();
 	register_actions ();
 
-	content_right_pane.remove(content_right_vbox);
-	left_attachment_button.set_sensitive(false);
-	bottom_attachment_button.set_sensitive(false);
-	right_attachment_button.set_sensitive(false);
-
 	/* monitoring */
 	_auto_input_button.set_related_action (ActionManager::get_action ("Transport", "ToggleAutoInput"));
 	_auto_input_button.set_name ("transport option button");
diff --git a/gtk2_ardour/trigger_page.cc b/gtk2_ardour/trigger_page.cc
index 5ef25a44b1..c805971781 100644
--- a/gtk2_ardour/trigger_page.cc
+++ b/gtk2_ardour/trigger_page.cc
@@ -77,8 +77,6 @@ TriggerPage::TriggerPage ()
 	load_bindings ();
 	register_actions ();
 
-	left_attachment_button.set_sensitive(false);
-
 	/* Match TriggerStrip::_name_button height */
 	ArdourButton* spacer = manage (new ArdourButton (ArdourButton::Text));
 	spacer->set_name ("mixer strip button");