I was taking a look at weaponabilities.config at the combo finishers don't appear to be be listed. My question is two part: Where are they listed if anywhere, and can we make custom combofinishers?
All existing fistweapons use a fullpath reference to their finisher. If you follow that path (/items/active/weapons/fist/combofinishers/" you will find all existing finishers, and they can serve as your framework for designing a new one.