Well we currently can filter for multiple topics & categories:
category:bug,featuretopics in the bug or feature category including all subcategories
=category:bug,featuretopics in the bug or feature category excluding all subcategories
tag:bug+featuretopics tagged both bug and feature
tag:bug,featuretopics tagged either bug or feature
…and we can also prepend “-” to exclude a factor.
But neither Advanced Search nor Topic List Filter supports the boolean operation “OR”. You could write up a Contribute > Feature request if you’d like.
References: