It would be nice if there was some way to have this add-on work with multiple messages selected. i.e. if you select two or more messages, check to see if any filters apply to all of them. I sometimes have a bunch of mail in my inbox from the same person, that I want to file away all at once, and I will select them all and then realise (as I keep forgetting) that the filter add-in won’t show a button under these conditions.