I use tags to identify my albums and my wife’s albums. I also have a bookmark for each. It works nicely. We can each easily get to our own album collection in Roon, and it also handles overlaps where we like the same thing.
If I go to the tag box at the top left of the screen and select both my tag and my wife’s tag, it comes up with a result that is two less than the total number of albums in the collection. Obviously, I skipped two albums when I did the tagging. But how to find them? It would be nice if I could do a search for all albums that don’t contain the tag “Fred” or the tag “Martha”, for example. But I don’t see any way to do that. I obviously do not want to go through each album separately and find the two with the missing tags.
If there is no way to do this, consider it a feature request. 
If there is something I am missing, I would appreciate some advice. Thanks.