Idk this idea just popped into my head
Philtre of Visibility(or something like that lol)
Basically you tame a pet, it has a carried trait and you use the Philtre to make it visible? There could be a limit on how many times you use one. And maybe there could be a themed version too, idk.
Maybe also a Philtre that turns the visible into a carried....(how would that be useful though?)

No support from me.

I believe this is actually something thats been suggested before, but the biggest problem is this would really hurt breeding. As of right now, multi-vis pets have at least some value because it does take effort to breed those traits. Something like this would eliminate the need to breed thee things, and make it way too easy to get multi-visible pets.