I posted this inside a thread over in the Suggestions forum.. but it's actually a bug:
I did a combination of searches on the word "subforums":
- Selected "All Forums", Result: correct listing of two entries in subforum 1 and subforum 2.
- Selected the category "Testing Forums", Result: incorrect results of nothing found.
- Selected "Test Forum 2", Result: Nothing found. This is the nesting search capability I'd like to have added.
- Selected "Subforum 1", Result: correctly found 1 entry
- Group Selected "Test Forum 1, Test Forum 2, Subforum 1, Subforum2", Result: Correctly found 2 entries.
- Group Selected "Testing Forums category, Test Forum 1, Test Forum 2, Subforum 1, Subforum 2", Result: incorrectly found no entries
It appears the category search doesn't work, and even corrupts the search if the category is added to a group search.