STEPS TO REPRODUCE 1. Add network:/ and trash:/ to Kickoff/Kicker/etc as favorites. 2. Right-click on them > Remove from Favorites. 3. Restart plasmashell or the computer. EXPECTED They're gone. ACTUAL They're still there!
Related to https://bugs.kde.org/show_bug.cgi?id=385814
Yeah, apps don't return, so Bug 385814 is fixed for me. But these KIO worker URL items return after being deleted.
Must have been an "old database" problem; after manually deleting these entries from the database and doing it again, the issue no longer recurs.