I commented earlier that <"Search" only locates keywords that are in Notes within the Category being searched. It does not find keywords that appear in the names of Sub-Categories, or that appear in Notes within Sub-Categories.>

I was wrong. I think that the Preferences file was corrupted. After I trashed the file, the Search function worked as it should. It can operate on a single category, or on all notes. That said, Iappologize for my mistake and revise my rating to an unqualified 5 Star.