March 1, 2024 - how to wire a 4 conductor sub feeder into a main panel 8/3 40 amp circuit 240 volt

Are you gonna build a false wall in front of all those exposed wires ?

The ground and neutrals do not bond together at the main panel. They bond together at the service disconnect at the meter. Hopefully you have a meter base with a main disconnect.

Poor skills and production values. Waste of time to watch. No professional strips the outer shield of cable like you did. Amateur.