The Window menu deals with the layout of the different windows, and their visibility.

□ Audio/MIDI SetupShows the Audio/MIDI Setup window, where the sound system configuration can be modified
Editor
Show EditorSwitches to the Editor view
HideHides the Editor, hence showing the Mixer when the windows are attached
AttachIf the Editor window is detached, separated from the main window, attach it back
DetachIf the Editor is attached to the main window, detach it (makes the Editor a separated window, useful for multi-monitor setup)
Mixer
Show Mixer/Hide/Attach/DetachSame as for the Editor, for the Mixer window
Recorder
Show Recorder/Hide/Attach/DetachSame as for the Editor, for the Recorder window
Preferences
Show/Hide/Attach/DetachSame as for the Editor, for the Preferences window
MeterbridgeShows the Meterbridge window, that displays all the tracks' meter at once and their recording status, and is very handy for multitrack recording
□ LocationsOpens the Ranges and Marks window, a single point of control for all range and location markers
□ Big ClockOpens the Main Clock as its own separate (and huge) window, which is helpful when recording
□ Transport ControlsOpens a floating Transport Bar as its own separate window
□ Virtual KeyboardOpens up the virtual MIDI keyboard. If a MIDI track is selected (or many), this keyboard can be used as an hardware device would.
□ Video MonitorIf a video has been imported in the session, opens a video window (namely, Xjadeo), synced to the timeline
□ Audio ConnectionsOpens the Audio Connection Manager window, a way to make connections to, from and within Ardour's mixer
□ MIDI ConnectionsSame as above, for the MIDI connections
□ Tracks and BussesOpens the Tracks and Busses window, which is a shortcut to many tracks/busses operations (routing, effects, …)
□ Bundle ManagerOpens the Bundle Manager window, allowing to create and manage Bundles, which are a way to simplify connection management, by defining groups of ports
□ Plugin ManagerOpens the Plugin Manager, a dedicated tool to deal with plugins, add new ones, and troubleshoot all plugin-related issues
ScriptingOpens the Script console window where LUA scripts can be edited and run
TemplatesOpens the Template Manager window, for both sessions and tracks templates managment
□ Transport MastersOpens the Transport Masters window, where all the timecode sources are shown to be selected and/or synchronized
□ Keyboard ShortcutsOpens up a Keyboard Shortcuts window, which allows for easy creation or modification of any keyboard binding
□ Plugin DSP LoadOpens the Plugin DSP Load window showing all the active effects, plugins, etc… with bar-graphs showing the induced DSP load latency
□ Performance MetersOpens the Performance Meters window showing the current system's load. Considering the buffer size, how much of it is spent idle or processing, and what takes processing time (engine or session)
Midi TracerOpens the MIDI Tracer window, allowing to follow each and every MIDI message entering or leaving Ardour
□ LogShows the Log window, where Ardour lists useful information, warnings and errors