This is a script for KWin, not a replacement for KWin (you use the script with KWin)

Very nice to hear some feedback! I see that the “shifting windows by moving them” thing is pretty popular, I’ll have to look into something to do that.

The “no official support” thing is really only there because I don’t drive X11 and don’t test for bugs there myself. Anecdotally, it works about the same feature/bug-wise.

https://www.reddit.com/r/kde/comments/6uv167/is_there_a_kde_equivalent_to_gnome_boxes/

Tldr - Virtualbox uses qt5 and virt manager is also supported