How do I create and use virtual desktop for on screen only?
Set up virtual desktops in System Settings as you like, and check the box to allow switching independently. You won’t have these only on one screen, as far as I can tell, but switching can be per-screen.
)
Set the option as in my screenshot, assuming you are on Plasma 6.7.
Then hit meta-F2 to switch to the second screen, and meta-F1 to switch back.
Or ctrl-meta-left/right arrows to cycle. Check your keyboard shortcuts to make sure these are correct, or to change them if you wish. (Search for “desktop” )
Perhaps a link to the shortcut options might be a handy thing for the Plasma devs to add to the configuration page…
This is what I was looking for.
(did not find this anywhere, not in help, not doing a search. a very well-kept secret)
Yeah, while a keyboard shortcut seems like the automatic and logical thing, I know from my own brain that this is not always the case. Let alone which shortcuts.
A lot of us have never really used virtual desktops at all. A tiny helping had, a little 
icon to show the shortcuts, or something.
Yeah. for my daily work I would never use it. It makes you very unproductive. But I’m preparing a demo/course in which I need to switch between two full screen applications frequently and virt desktops seem the natural thing.