So the current DC panel is supplied by 10AWG wire? And you have never had more than 30A of DC loads going at any one time? That's seems really unlikely.
Dunno what to tell you. There are exactly four wires coming out of the battery compartment in the original configuration. Two of them are the #2 AWG leads that are labeled 'GEN START' and go directly to the generator starter. Two of them are #10 AWG labeled 'BATT +' and 'BATT -'.
In it's stock config, there just aren't a lot of DC loads on at any one time. Just sitting there 'steady state' running nothing but the DC control board for the fridge and small parasitic loads like the CO detector, it's maybe 1.5-2A draw. Obviously a little more if running the roof fans or charging something from the 12v outlet. See the attached PDF for the factory supplied load center drawing.
I suppose in theory someone could attempt to extend the slide *and* the awning *and* raise the camper on the jacks, all at the same time, whilst also running the furnace blower, the water pump and both roof exhaust fans... but you'd have to be pretty talented to manage all that. Kind of like you could, in theory, run the air conditioner at the same time as the microwave and a toaster plugged in on the counter, on the AC end of things. It probably wouldn't work very well for very long, even on '30A' shore power.