The way 485 addresses devices is... just to prepend an address byte. Or bytes. Whatever you want, really. The link layer, which RS-485 is, doesn't care.
As others have said, RS-485 isn't really the way to do this. It looks like RS-232, but it's just close enough to mislead you while being far enough away to be a total nightmare. For example, any bus collisions have to be handled in software. A driver that has to recognize and deal with bus collisions looks very different from one for a dedicated line.
This rabbit hole is probably not worth going down.
As others have said, RS-485 isn't really the way to do this. It looks like RS-232, but it's just close enough to mislead you while being far enough away to be a total nightmare. For example, any bus collisions have to be handled in software. A driver that has to recognize and deal with bus collisions looks very different from one for a dedicated line.
This rabbit hole is probably not worth going down.