Connect pins with same pin designator in Altium footprint
I once made a diode with a four-pin anode, all of which I wanted to connect together. You could connect all of the anode pins separately, but I would recommend giving them different pin names (i.e. 87a, 87b, 87c) and treating them as separate pins on the PCB layout. However, on the schematic, lay the three pins one on top of the other so it looks like just one pin. Altium will see a wire connected to the "one" visible pin as connected to all three pins, and will tell you to route all of their corresponding pads together. You will need to go into the pin editor on the schematic, though, and make sure you change the pin names and which pads they connect to. That's probably the most elegant solution.