I wanted to change the wallpaper and have a .png file I wanted to use. In Cinnamon it’s easy to do, in KDE Plasma it is a bit more convoluted. In Quick Settings I clicked on Change wallpaper, then changed the location to Documents because that is where the png file resides.
I got the wallpaper change alright, but now all the files and subfolders of the Documents folder are shown on the desktop, incl. confidential ones. If I delete them from the desktop they are deleted from the Documents folder too.
This is what I get when I go to the Documents folder in Nemo: