There is a tutorial on how to add new parts in the manual.
I found it, thank you! I kept bouncing between the links that said "Wiki", "tutorial", and "where to ask for help". I didn't realize that "software's documentation" was actually the manual, whoops.
Edit: Was quite simple to do, actually! I'll be able to split off armor and gloves quite easily, and even noticed that Male Top9 could make a nice vest. I'll have a nice collection of fantasy pieces before the end of the day.