I think we’ve all been there… Best way to use additive animations effectively - #12 by Panuchka
Is there a reason why you need to chop off the head, arms and legs? I’ve been trying to get a following workflow myself:
- Model the character
- Rig the character (I’ve now used autorig pro)
- Parent the model to the rig
- Add 10000 animations from Mixamo to the rig using autorig pro retargetting
- Export glb
The only thing I haven’t figured out is in the thread that I posted… But I hope it will be a bit silver bulletish solution, at least for my problems. We will see 
The main takeaway is that I store the skeleton and the animations and the mesh itself in single file. I do also have clothing, and separated body parts that can be chopped off if they are under clothing and not seen 