I have installed KDE Neon User Edition 5.21 but in the System Preferences - Workspace Behavior - Desktop Effects - Desktop Cube section - cannot change the background to a custom one in the Desktop Cube, the box for mark it as an option and put some own wallpaper in the background.
Do you know in which part are the configuration files of this part to be able to configure them
I leave a screenshot of the configuration window where the box to check it does not appear.


https://imgur.com/nH7PiXO