Did they leave you with a hyd outlet somewhere around the 3pt?
Look around under your right foot, and see if you see anything like this.
There is a PB hard line from your loader valve 080 in the schematic that goes back to the 3pt.
You can cut that line and use compression fittings and add whatever valve you want.
The PB line would go to the IN port of the 3rd valve, and the OUT would go to the 3pt.
How do you plan to use the 3rd function valve.
You could also add remotes for whatever also.