Currently mounting and dismounting a horse is tied to the Interaction hotkey (Defaut "R" key). However this frequently causes problems. Such as trying to mount or dismount in a crowded city street. Instead of mounting or dismounting you instead interact with the nearest random NPC and you can to keep adjusting your position until you find a spot you can dismount. The same happens in the wilderness if your mount is near a resource that can be harvested, you often start gathering instead of mounting when pressing R.

This issue is compounded with the new Horse teleporting to you when turning in quests. Recently I was turning in a quest to an NPC that was standing under a canopy. Turning in the quest caused my horse to teleport right into the NPC. Then, when I tried to interact with the NPC again, it caused me to mount my horse...UNDER the canopy. Since the horse and I were too tall, I could not move out from under the canopy and I was now stuck too close to the NPC to dismount because "R" kept interacting with the NPC. So I was forced to use the "Escape" feature and get teleported somewhere else then run back, for no reason other than bad key binds and teleporting horses.

All of these issues could be easily fixed by making the mount/dismount key something different than the normal "Interact".

Good tip, but what about getting back on?

shouldn't be a problem, either move camera to where ur interactions is towards horse or use mouse movement to select horse

if ur horse is stuck you can move out urself and call it using horse whistle

As long as the interaction wheel is visible when you are next to your horse, R should mount you.