Guild Wars 2

I transmuted my pact weapon appearance onto an ascended weapon.

To have access to the pact dagger skin, do I need to split it prior to tomorrow’s patch or will I be okay?

I ask because I want to use incinerator for both my main and offhand weapons, but I don’t want to lose my dagger skin by marking Incinerator over it, and I don’t want to just scrap an ascended weapon either.

You don’t need to split it. You’ll unlock both skins tomorrow: the skin that you currently have, and the last skin the weapon you "skinned’ had. Ie: if you had, say, a Lyss with it’s base skin, and transmuted that onto an acended weapon with it’s base skin, you would unlock Lyss, and the ascended pistol’s skin. If you transmuted a base lyss onto an ascended pistol that had previously been transmuted with, say, Brandt’s skin, you would get lyss’ and brandt’s skin, but not the ascended pistol’s skin (unless you had another ascended pistol, of course)