I have been googling away but I haven’t found an answer. Say I import a model and this model has a slider that goes from skinny to obese customizability. These are of course morphs. I import some clothing items that goes to the same exact skeleton and uses the skeleton with the morphs. How would I transfer or connect the morphs to that shirt or do you have to go through a different process?
You need to create the morphs on the shirt in some external DCC. Ideally, they should have the same names as on the main model.
Once you have that, you can use Set Master Pose Component or Copy Pose from Mesh to have the shirt automatically use the same morph values as the base model. See Working with Modular Characters | Unreal Engine Documentation