Steps to reproduce: 1. go system-settings->Shortcuts->global shortcuts->plasma->Activate Dashboard Widget and change combination 2. remember date ~/.config/kglobalshortcutsrc changed. logout 3. login and check date ~/.config/kglobalshortcutsrc changed. Shortcut doesn't get saved. It does persist when changed right clicking on launcher and selecting shortcut there. Reproducible on opensuse leap 42.3 and ubuntu 18.04. Suggestion: to keep old shortcut as alternative one unless it's default one.
*** This bug has been marked as a duplicate of bug 300532 ***