Created attachment 148617 [details] window in middle Tested on wayland, haven't tested on X11, but in a multiple monitor setup, if I put a window across both monitors ( ex: half of the window is in one monitor and half in another ) and press an effect like overview, the window gets duplicated in the effect. Also, when switching virtual desktops vertically, the window gets cutted in half ( only shows part of the window in one monitor. the rest of the window then just magicly reappears after the animation ). Sorry for doing the example with screenshots, but I am having troubles with obs.
Created attachment 148618 [details] window in middle on overview
Those are two different bugs. Let's use this one for Overview; can you file a new one for the Virtual Desktop issue and put "453479" in its "See also" field?
This seems solved in latest kwin (6.0.4). The multi monitor window appears only on the right most monitor only now for me. (so, in just one, which I am OK with it.)