@tgreer Thanks for your reply, and thank you for merging my post into this one. I hadn’t found it, but seems to be similar indeed!
Your suggestion am sich did not work for me, I tried several variations:
>-organizationid:00000000-0000-0000-0000-000000000000
>-organizationid:"00000000-0000-0000-0000-000000000000"
>-organizationid:00000000000000000000000000000000
All with my own GUID, not the empty one, of course. None of them seemed to filter anything.
What did work was:
>-organizationid:* // will search for all Vault items that do not belong to an Organization.
And it works well enough as a workaround. At least for me, I don’t think I can explain this to my non-technical colleagues. So a proper feature or filter would be much appreciated, still.