After swiching to Plasma 6 Meta/Win button isn't recognized at all. It means when click to bind the key nothing happen, no key pressed. It works correct in Plasma 5 could be it because of khotkeys removal?

For these kinds of issues, make sure to test with a new, clean user first, it might be an issue with one of your existing rc files.

Just test with clean user, just same. When I click to add new shortcut, Win key isn't recognized at all, like no key is pressed.

Interesting could it be a kernel/firmware issue? Just test xev in Wayland and X11 (new clean user) key is not registered like Fn (laptop here) just no key code or any event registered.

Fn+F2 locks it, never used so far