I'm giving the OP the benny of the doubt. According how/who you want to believe path direction, current leaves from ground to the hot side. Case in point, look at the (+) cable glowing.
I'm trying to say the current wants to find the shortest path and if you have all your 8 paths free, then am I trying to say the engine may be sitting on a pad with paint on it, not bare metal.
And it's now not about the OP but your diagnostic path to hot cables/no starter motor spinning.
What I'm trying to say is, though this may not be the problem, and say the starter froze, all that current is backing up and at that hot spot, I say, know your good known paths, meaning, do the work.
This is tail chasing time. How fast can I make a ground is that jumper cable, if not 2 of them so one cable set is used for battery posts to ground/start and loophole the grounds at the trans to engine to frame and that sub-system. So to make the fastest path, it's the quick and dirty jumper cable(s)> if a hot bike cable turns cherry red = No 8 pad points needing cleaning. That's what I meant. No change in glow it is not the ground (jmp-cbl) system if those cables get hot = Look elsewhere like swapped battery cables around at the battery.
See what I meant by using the jumper cables to pin the tail on the donkey?