AnkiDroid custom study: support both intersection and union of tags

For some reason the UI wouldn’t let me include a link in my original post. The other request is here:

I saw filtered decks suggested before, but as far as I can tell this doesn’t work in AnikiDroid. The AnkiDroid filtered deck UI doesn’t seem to offer a way to filter on individual tags, or even to restrict the filtering to a single deck. Maybe I’m mistaken?