Somehow I have gotten Ardour (5.5.0 on kxstudio 14.04) into full-screen mode (hit some combination of keys by accident, I suppose) and I cannot figure out how to get out of it. Scoured menus, reference manual, forum, but find no mention of full-screen mode at all (other than ctrl-alt-f) which just toggles between full screen with KDE panel visible or not). Any suggestions?
same here (in the latest mixbus though) 
the mixer always goes fullscreen covering the taskbar… Manjaro linux, xfce desktop
In my case, the combination Ctrl-Alt-F (full-screen editor) and Ctrl-Shift-F (full-screen mixer) doesn’t work if I switch a none-English mode of the Keyboard Layout. If I change the Keyboard Layout back to English (in my case I use Ctrl+Shift combination) - the hot keys begin to work well.
(I also use KXStudio 14.04 with KDE)
Shift+Ctrl+F toggles the mixer from full screen mode. You can also go to “View” and uncheck the box for “Maximize Mixer Space”.
Thanks for comments, but none of these suggestions help. Ctrl-Alt-F (full-screen editor) just toggles whether the KDE panel is visible or not (when visible covers the lower edge of Ardour), and Ctrl-Shift-F (full-screen mixer) doesn’t do anything. Not sure what mode my keyboard is, but would probably be English since I never changed it. Anyway, under no circumstances do the edges of the Ardour panel allow you to pull on them to reduce the size of the panel. All my Ardour sessions are now full screen, so it seems once Ardour goes full screen it will never come out of it. I wonder if there is some option in ~/config/ardour5 which could be changed, but so far I don’t see anything obvious. A silly but annoying problem.
Does KDE already use Ctrl-Alt-F for something else? I don’t use KDE, but I’ve noticed window manager key bindings may override those in applications. I had to disable some of the WindowMaker key bindings before Ardour would respond to them.
Another thing: what happens if you move ardour5 config file somewhere else to hide it and start Ardour with an empty config?