I am using the KDE desktop on Opensuse Leap 15.2, and I have problem with display settings resetting every time I logon.

Specifically, the wallpaper is changed to black and the icon layout is changed to horizontal from vertical and the icon size changed to large. The keyboard layout is also changed - @ and " are transposed and £ is $.
I change these all back and everything is OK until I close the computer down. On restart the settings are changed back. I tried creating a new user as a test and this does the same.

How can I ensure that my desired settings are retained after closing down? I also had the same problem with another computer using Opensuse Tumbleweed so I think it is a KDE problem.

Do you save the desktop settings on logout? Make sure your home is fully writeable, too

Every once in a while, something like a full screen game running at a lower resolution than my desktop, throws my desktop icon placement off.

On my system - plasma 5.20.5 - many of the desktop settings, such as icon placement, are in $HOME/.config/plasma-org.kde.plasma.desktop-appletsrc

I wrote a little script that makes a backup copy of that when my user logs in. When needed, I logoff from KDE, restore that applesrc backup, and log back on to restore my desktop layout. Kind of a hassle, but usually easier than manually setting everything back.