The weapon transmutation panel does not perceive slot II, swap weapon. I use Sword/Axe on slot I and Longbow on II. I was trying to skin the bow, but all I got were sword/axe skins. Closed transmutation panel, swapped on longbow, I’d still only see sword/axe skins. I had to remove my sword and axe and move my equipped longbow to slot I in order to transmute onto it. Not sure if bug or designed this way, but it can be confusing at first. In a bind over transmuting underwater weapons too.