Returning Outfits
Just…use the costume consumables. Using one unlocks the outfit for all of your characters on your account.
You receive several of them from the Black Lion Armorer because you get one for each part of the costume: Boots, gloves, coat, hat. That way, if you deleted (accidentally or intentionally) any of the pieces, but still had at least one, you’d unlock the full outfit.
So, if you’ve traded in the old town clothes version for the consumables, go ahead and use one, then you’re free to discard the rest, as there’s no use for them. (Since you can’t “unlock an outfit twice.”)
~The Storyteller – Elementalist – Jade Quarry~