If you have marked your favorite tags as such, then you can use the following two operators, as explained in the help center:
intags:minereturns only posts that appear in tags you have marked as favorite. (If you don't have any tags, this operator does nothing. For better results, update your preferences.)is:questionnarrows results down to just questions [...]
So, if you put both operators into the search box, then you should find all questions that appear in tags you have marked as favorite.