Hello everyone, 

Is there a way to create customized clothing through the deleting and joining of vertices in CC3? I know I can do something similar to that in blender, but I don't want to import my character into blender until I can figure out why both of her eye occlusions are completely white. I want to be able to combine the hoodie and the sash from the essential clothing pack to create a type of cloak. Here is a picture for reference: 

 
Any hints would be appreciated. Thanks.

CC is not a mesh editing app like Blender. So no, it is not possible to do it in CC.
But you should not care how eyes or anything else appear in Blender.

You use it only to customize a cloth and bring it back to CC. You then save the customized cloth in CC, apply back your original character and apply newly saved cloth to it.
Then fix cloth materials.

Or export amended cloth only from Blender, import that cloth to CC as an accessory and then Transfer Skin Weight.

Either way work just fine.