Window Menu

Item	Shortcut	What it does
Main Viewer	—	Brings the Main viewer to the front and gives it focus. Only listed when the Main viewer is currently visible.
Floating Viewer 1, 2, …	—	One entry per currently-open floating viewer (View → New Floating Viewer). Clicking an entry brings that window to the front. A checkmark shows whichever viewer last had focus.

This menu is rebuilt each time you open it, so it always reflects whatever viewer windows are currently open.