I can add another use case: I just wanted to empty the trash and got the question, whether I want to delete the indexed items, too. Well, I would like to see them first, and I started to build a smart group…
As an alternative approach I can look at the trash and sort by attribute “Path”. The imported (non-group) items presumably start with a ./.
A couple of those items were still in the Finder (and belong there), other items were no longer in the file system. So I wanted to manually deal with those items (move out from the trash since they are still valid files, hard-delete because they should be deleted). But I could not find a way to selectively manage the items in the trash.
Solution: don’t empty the trash 
If I miss something, I welcome any hints.