with sims logic the horse probably goes inside the backpack and from there can be placed on various horse related activity items or they can be placed down anywhere like the bicycles
or both
at home theres probably some item to blob your horse on to take care of it the way we have the sheds
I'm hoping that this time its not a shed though but something that can be built around easily
if we have wild horses those probably won't go everywhere like in ts3 but probably spawn at particular point in new world similar to how greg spawns in certain place