bus bar?

I am not sure what the extra wires go to, I need to trace some down but right now there are a few extra wires plus the solar wires for my portable set up. I was even thinking about just a pos and neg stud mounted behind the battery's on the trailer frame so all I would have would be a pos, neg and parallel cable on the battery's. I would also run my solar cables to the battery posts as well.

I guess you have a scenario that would make it easier with bus bars but I was trying to conceptualize the situation and can't get past that the fastener count would remain the same--at least two fasteners for every bank (+,-) and the terminals between either parallel or series connections.

FWIW, I do have busses and they are real slick for connecting battery power to solar controller, inverter, and converter. I made my own:

Yes lots of people here do that. I use the Trimetric shunt as my negative buss, but it can run out of room to stack terminals under that one bolt, so a secondary buss before that might be needed.

No, but this weekend I bought a battery disconnect switch. You could (as I will) just hook everything on the positive side to the switch and then just remove one cable going from the battery to the switch.

My bank is four group 31's in parallel - I thought about using buss bar or hammered flat 3/4" or 1" copper pipe, but decided against it. Seeing how things move around in my RV while it's bumbling down the road, I figured the #0000 cables were stiff enough and that a ridged connection between the batteries would be asking for trouble. they might not break anything I could see, but what if it placed stress on the post to plate connections inside the battery?

It sure would make it cleaner looking, but looks aren't everything - especially since I don't have to look in there that often, just every six months or so to check the torques on everything.

No reason you can't do that as long as the positive bus bar is covered/protected to prevent accidentally shorting it to ground.
I have not done it. My battery only has a single wire to each post and is distributed down stream after auto reset circuit breakers.