I inquired about this when someone asked about Eris.

Ganymede and Titan both outer planet moons, are larger than the rest of these bodies. Mercury, Callisto, Io, our Moon, Europa, and Triton all larger than Pluto. Nine bodies larger than Pluto, seven not used at all. If size does not matter, why aren’t these bodies used for astrology but much smaller asteroids and a comet (Chiron) are used?

I am unaware of anything assigned to the outer moons or other objects. Some of these have high angle orbits so they do not enter certain signs at all.