I have been enjoying my warlock. It seems that I cannot transmog my new 1-H sword to the ‘Atumbra, Shadow of the Cosmos’ dagger which I love the appearance. In the other classes that I play, transmogging among weapon types as long as they are the same category (1-H to 1-H, 2-H to 2-H) and usable by the class works great. It seems like this is an oversight.
As far as I know, you can’t mog a sword to a dagger or vice-versa, unless it a Legion artifact. Any weapon can be transformed to a Legion artifact provided its in the main-hand slot.
Can’t transmit a dagger into a sword.