issue: Lenovo t440p laptop with up to date LEAP 42.1, plugged into docking
station but showing screen on laptop screen. When pressing FN+F7 (the change
displays hardware key) the screen is suddenly mirrored. Interestingly, while
laptop screen is 16:10 and attached screen is 16:9 the resolution chosen by X
is 4:3. Not nice, but not the problem. When pressing FN+F7 again, the attached
screen becomes the main screen with the correct resolution. However, the
background image has been reverted to the default black one with the green
light bulb.

expected result 1: no change of background when changing screens.
expected result 2: well, starting the appropriate KDE application to manage
screens might be appropriate too ...