I've been struggling with the Plasma desktop as I can't set it's icon through the application editor... I've succeeded this task on another Debian install on a different machine... Yet on this PC it's been impossible to set it's name or it's icon... I tried purging and reinstalling all the desktop environment, I'm doing the same steps on both machines but it doesn't work on this specific one... Does anyone have any idea?

how about some more information about the exact Plasma version and the Desktop settings (e.g. whether you use the Folder View or not) ?