There is a way to make several pins have ie. name "GND". Name the pins "GND_1, GND_2 etc. Then modify the text properties to "Hidden" and then add manual text "GND" to the pins. That way, you can name them anything you want. But IMHO it may make a netlist review more difficult. Assigning other names like xvibe suggests is also possible, but this will also make netlist review difficult. Mixing supply voltages in a complex design is easier when all pins have "real" names and supply voltages can be clearly seen in the schematics. Quite a few supportnet tickets I have seen deals with netlist problems that comes from net assignments that does not match when doing CDB.