Cancel full screen mode in Firefox without F11

How do I cancel the full screen mode in Firefox (currently V70) without using the F11 key on the keyboard?

I know I can do it through a virtual keyboard (see my own answer) but I'm looking for an easier way.

2 Answers

Move the mouse to the top right (or left) corner of the screen; click on the hamburger "menu" button (displayed as ≡) and select the double arrow (something like ⤢) at the right of the line starting with Zoom to toggle "full screen" mode.

Not a solution but a possible workaround in some cases: use a virtual keyboard. But this is tedious to get to (lots of clicks) if you haven't set it up before hand (e.g. on a new system).