When I click "Starred" in the left column, it currently only shows starred (IMAP "\Flagged") messages from the Inbox.

It would be nice if it would show flagged messages from all folders.

More generally, perhaps "Flagged" could be an option in the Advanced Search box, in the same way that "Has attachments" works. That way I could search for it in single folders or all folders, or perhaps in combination with other attributes (for example, it would then be possible to search for all Flagged messages from a certain address).