There are way too many posts that have been flagged in StackOverflow, or at least that has been my perception for the past few days.
I believe it would be useful to add tags for filtering these posts. There are posts that one could come back to later, because it is not within one's domain of expertise, but reading such posts often takes time. Filtering on tags would make it easier to sift through flags. It exists for the page where new user posts (and first and late answers) are reviewed, so I thought it should be present in the Flagged posts page as well.