I've found a few topics asking for the same thing, but none from 2021 (and all were just people saying "yea, I'd like this too!"), so, I just thought I'd put the idea back into the public consciousness. I just grabbed a 5th horse (not even the final horse I planned on getting after doing research (new player, btw)), assuming you could fill up EACH stable in the game (ie: they would operate like literal physical stables and not 1 single linked stable.....especially because they sell different horses...great consistency there). I was really surprised that there wasn't already such a seemingly simple mod on Nexus already :(