I entered the latest RD TABS version into "full screen" (no menus etc) mode but I can't seem to exit the mode (what is the hot key to toggle?).
When I exit and come back in RD Tabs remembers the mode. Brick wall

The only thing available is the PLUS button to add a tab and my current open tabs.

Hotkey is F11.

If you hover at the top of the screen, the menu bar will appear. If it doesn't, try clicking once (that's a different option in the settings).