You're on the desktop. Then if you press the keys Ctrl+Alt+Esc at the same time, it appears a new cursor to close any application. Now if we click on any part of desktop, everything is darkened as the process plasmashell is closed. Do you think Operating System: Manjaro Linux KDE Plasma Version: 5.19.5 KDE Frameworks Version: 5.74.0 Qt Version: 5.15.1 Kernel Version: 5.8.11-1-MANJARO OS Type: 64-bit Processors: 8 × Intel® Core™ i7-8565U CPU @ 1.80GHz Memory: 15.4 GiB of RAM Graphics Processor: Mesa Intel® UHD Graphics 620
I mean technically it killed the thing you clicked on. :) That's what it does. :) If you want to dismiss this thing, you can hit the Esc key on the keyboard.