Electrical question 2018 F350

Does anyone know specifically where the blank tab off the relay box connects to internally? It goes hot when the acc is on. 2018 F350 diesel.

The other connects straight to the right side battery and powers the relay box best I can tell

I'm trying to find the best place to connect 4 gauge wire to run directly back to my Lance camper's charging relay for more charging from the alternator.

I have a connector and plan 4 gauge all the way to the battery after the blue seas 7610 and of course a fuse right of where I tap fpr the power from the truck.

Thanks!