Answering your comment, but it's very related to your question
To clarify, the original setup was a star, orbitted by a planet, which
is, in turn orbitted by moons on a horseshoe around it. What I'm
saying is would it be more feasible to have a star, which is orbitted
by one large mass + other objects sharing a horshoe orbital with that
large planet, rather than being it's satellites? Switch it from them
as moons, to a series of planets on orbital with a giant. Usually the
horseshoe orbit would only have two objects, but is that necessarily
the case? Could it, instead be one large object with multiple smaller
If you want a planet with a lot of moons, increase the planet's hill sphere. That can be done by increasing the planet's mass or moving the planet further away from it's star. If you need your planet to be in the Goldilocks zone, make the star bigger, just don't make the star too big because it's life will become too short for habitable planets to happen. If your star is over 2.5 or 3 solar masses it's life may be to short for the planets to form and moons to cool.
Even with a bigger hill sphere, A dozen is pushing it. Orbits need distance between them for long term stability and 12 probably too many. If you multiply each distance by 3/2 for resonance and even if you don't have resonance, that's a fair enough ballpark estimate, then the outermost moon is 130 times as far from the planet as the innermost and the innermost moon can't be too close to a large planet, or should undergo fairly rapid tidal forces drawing it inwards or outwards.
If you make some of them teeny and distant then 12 moons is easy. Jupiter has dozens of moons, but just 4 large ones.
Sharing orbits in a horseshoe (or Trojan) doesn't help you add moons because a horseshoe orbit would be perturbed by near-by large orbiting objects. In other words, you need to create extra space around two moons sharing an orbit, so you've not really increased the total number of stable orbits for large moons by putting two in a horseshoe. Now if you do large and tiny, you can have several tiny, but large and large and some measure of stability, two is the limit.
A horseshoe orbit is very similar to a Trojan orbit. If the two moons orbital periods are close enough, they get caught in each other's saddle points and never cross. If they're a little bit further apart from each other, then the catch-up moon can pass through the saddle point and the two moons can switch places (kinda-sorta), as they undergo the horseshoe dance.