You can make smart collections at any level you desire.
- tag: filler - collection of all commercials and all trailers
- tag: filler AND tag: commercials or tag: (filler AND commercials) - all commercials only
- tag: filler AND tag: trailers or tag: (filler AND trailers) - all trailers only
BTW if commercials and trailers are only presented as tags from this single source, there is no need tag: filler in the last two examples. ie tag: commercials will give all commercials only
Similarly,
tag: filler AND tag: trailers AND tag: G or tag: (filler AND trailers AND G) - all G rated trailers only (just tag: G if G is unique as a tag)