Child Board Filter

[Senkusha]

My site has a couple of "catalog" boards, meaning there is a board dedicated to generalized discussion about a specific topic, but there are also dedicated child boards for discussion of very specialized topics.

For example.  My site has an anime discussion section.  And one of the visions I have is a dedicated area for specific anime.  A home for fans of a particular anime, since the Age of Fan Forums has pretty much been ended by Facebook Groups.

But that leads to a problem.  Now I've got like 30 some-odd child boards and I've tried many different approaches to categorize or group similar anime together, however, many anime themes can overlap.  So I got to thinking, why not create a Tag system for Boards, instead of Topics.  I can create a tag filter, right now I'm thinking based on Genre, but it could be extended to include anything really.  And a member can select the Tags they are interested in viewing.

The database modifications aren't all that difficult, but I'm stuck at how to implement this into the SMF code.  I could use a dropdown box for a quick select on parent boards that have Tagged Child Boards.... but maybe I'm not understanding the construction of SMF enough yet, because I don't see anywhere in the BoardIndex.php where the database is queried to get the boards?