@Luca
Honestly, you don’t really need to know what each wire does. Just cut out the damaged section of one wire, repair it, and move on to the next. This way, nothing gets mixed up. I had to deal with over 50 wires when I was working on a Corvette build. Solderseal connectors will make the job a lot easier. Also, it definitely looks like a rodent issue.
@Raj
That’s solid advice. Fix one wire at a time and you won’t need to know what each one is for. But if you’re curious, just check the wires on the parts themselves (like the rear cab light, tail lights, etc.) and match the colors.
It could be from rubbing, but I find it weird that the harness in the cab would move around enough for that.