For me (Leap-42.1) holding down <Alt> while pressing first <d> then <s> brings up the Desktop Settings Dialogue box. I had removed the Desktop Menu and do not see how to get it back.
I think that something is broken or missing in 6520302’s plasma installation. I had problems with the mixed KDE-4 and 5 packages in the initial DVD installation and had to manually add the missing Plasma-5 packages from repo-oss, removing the conflicting and redundant KDE-4 packages to get e.g. Kmail and the rest of PIM to work. I suspect that the recent KDE update will fix this for new “Net” installs.
Maybe I have something broken but I would have no way of knowing that. I did get the Framework(KDE) update yesterday. I don’t use Kmail or any of the PIM stuff so nothing there I can check on.
Interesting that even though alt-d alt-s do not work, alt-d-s does work!! Whether I can remember that is another story.
As for missing stuff, I did not have any help available in Configure Desktop - System Settings. I don’t know if that was intentionally left out or not, I did have help available when I looked last week. Searching in Yast for Help showed khelpcenter5 v5.4.3-3.7 not installed. Now installed. Unfortunately, help for themes does not exist (yet).