In KDE Effects, there's effect called "Window presentation", it shows all windows when you hit Ctrl+F9 or point your mouse to upper left corner (... i believe this is a default behavior). In effect's, config, you can set desired action for left/middle/right mouse click on window or desktop. In action selection menu there used to be "Close window" action which was very handy to me to quickly clean my workspace, i had it under middle mouse button. Now it's gone.
I've tried to google why, but with no luck.

Reproducible: Always




I'm using Polish translation, in my description i've translated effect/action names back to English. Might not be accurate ;)