Last time I was creating manually routes and balance dimensions was in the good old 10.7 era. Almost nothing is changed in the datamodel for all the FF tables. I guess this is so crucial and omni-present in the core payroll engine, that nobody from development wants to touch it anymore.
The tables I added some lines were:
* FF_routes
* FF_context_usages
* FF_route_parameters
* Pay_balance_dimensions
To overcome sequence related problems, I simply use negative id numbers.