Created attachment 131944 [details]
Picture of the described behavior after switching user, then logging out

SUMMARY

When creating an additional session with KMenu -> Power/Session -> Switch User, when I complete the other user's session and logout, I am returned to my main login desktop (as expected). When I click Power/Session -> Switch User to log in again as a different user, there is an "unused" icon appearing in the choices. If I create additional sessions; logout; and create yet still newer additional sessions and logout; eventually, the "Switch User" screen becomes filled with these "unused" icons. Clicking on "unused" does nothing.

This is new behavior that began occuring in OpenSuse Leap 15.1 (which I use at home), but is still present in Leap 15.2 (which I use at work).

Not a show stopper. After a few "New User" sessions and logouts, I just restart the computer. But since this is new behavior, the only reason I report it is because of the possibility of unreleased system resources/memory leak/etc.


STEPS TO REPRODUCE

1. Using autologin (which I do), go into your main, personal KDE desktop. 
2. Click KMenu -> Power/Session -> Switch User, select New Session, then login as a different user. Do some work, then log out.
3. If you then try to switch users again, there will be an "unused" icon next to the "Switch User" icon.

OBSERVED RESULT
Extra icons each time I switch user, then log out, then attempt to switch again.

EXPECTED RESULT

This only started happening with OpenSuse Leap 15.1; something has changed.


SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: OpenSuse Leap 15.1
(available in About System)
KDE Plasma Version: 5.12.8
KDE Frameworks Version: 5.55.0
Qt Version: 5.9.7

ADDITIONAL INFORMATION

Again, this is not a critical bug, and should not be treated as such. But as I said, there is a possibility that some system resources aren't being released when the additional "new" users are logged out.