All good suggestions, - not sure how yours differs from the lj78 apart from engine, but there is a black plastic box engine bay/drivers side inner wing, with power stamped on it. As far as I remember there is only a large fuse in there, for a winch for example, I don't think there is anything else in there, but check. The fuses behind the panel you have found are not indicated on the diagram for windows, so is a mystery. I'm wondering if it could be a relay in there, also not indicated. You could maybe do a process of ilimination with relays by swapping them around one by one, but only like for like if there are several the same.
Apart from that, pull the individule rear switches, and with a meter or test lamp, check for power to each switch, you maybe need someone to operate switch/s with ignition on as part of this process.
I don't think it is the master switch on drivers door, as on my lj78 that locks/unlocks all windows.
I'm no expert, but I know from past experience, these 'little' electrical jobs can be a PITA.
Good luck !