I put this article in the label Story, because I don’t really know for sure when I can resolve errors in xfce desktop on Xubuntu 18.04 that I use. At that time, when I wanted to set a wallpaper on the Xubuntu desktop, right-click on the desktop didn’t work. Finally, I tried changing the wallpaper via Settings Manager in Xfce. However, that also didn’t work, when I chose other wallpapers, I didn’t see the wallpaper change on the desktop.

Source: LXer – Fix Xfce Desktop Error, Can’t Right-Click and Change Wallpaper