SUMMARY STEPS TO REPRODUCE 1. Enable Wobby Windows 2. Move a window and press alt+f4 (simply close the app) OBSERVED RESULT When the window that is currently being moved will be closed a copy of it will stay on the desktop EXPECTED RESULT There shouldn't be any copies of that window it should just disappear. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch Linux (available in About System) KDE Plasma Version: 5.26.5 KDE Frameworks Version: 5.101.0 Qt Version: 5.15.8 ADDITIONAL INFORMATION I haven't experienced that issue on older versions of Plasma.
Forgot to mention that the app should be closed while it's being moved.
Created attachment 155117 [details] Here is a screenshot with the "shadow windows" Spectacle and Steam became shadow windows
Restarting Kwin makes the shadow windows disappear.