I'm having a similar issue that I asked at the same time.
I'm attempting adding categories
Existing: Performance Parts By Vehicle >> Camaro Existing: Performance Parts By Vehicle >> Corvette
Attempting to add sub categories for each vehicle: Air Induction Engine Exhaust Etc..
For an end game of Performance Parts By Vehicle >> Camaro >> Air Induction Performance Parts By Vehicle >> Camaro >> Engine Performance Parts By Vehicle >> Camaro >> Exhaust Performance Parts By Vehicle >> Corvette >> Air Induction Performance Parts By Vehicle >> Corvette >> Engine Performance Parts By Vehicle >> Corvette >> Exhaust
I'm including parentIDs but having issues with categories being overwritten.