It's under the left hose, if you look at the bottom of the picture you can see the 7th hose. The light in the barn isn't the greatest. I looked through my manuals and found I have the loader one still and it does have information on it. That left hose off the top is the PB one.
If I am understanding the fluid flow correctly, the pressure side, the right bottom hose comes from the pump, the left bottom hose is the tank, the PB line goes back to the fitting and supplies pressure for the 3 point lift cylinder. That rear outlet I found breaks the connection between the PB line and that cylinder, so whatever is connected would need to also be a PB? That means I would also need a third line to the tank.
From what I have been reading, if I connect a center open spool to that outlet, then if I apply pressure to one side of the spool or the other, then there would be no pressure to operate the lift unless the spool has the PB. They don't make it easy.
So the easiest way appears to be breaking the connection from the PB fitting at the loader, run a line to the rear from there, then run another line from the rear that has a fitting that connects to the first one, and then that one connects to the block. If it is disconnected, then the rear lift would not work, but would not cause the pump to overload since the loader valve has a tank dump. Now does a splitter have 2 connections, or 3?