I tie my horse to the trailer, and when we’re in the mountains we use a high line. The high lines are permanent though, they are metal poles cemented into the ground. I sleep in the tack room of my trailer, but I’m a very heavy sleeper, and my horse is pretty well used to camping, so he’s fairly quiet out there.
The high line needs to be high enough to tie the horse above his eye level, and if they can move along the line or else are tied with friends, they seem to get a lot less fidgety.
I would like to buy the corral panels that clip to brackets on the trailer, so you can make a stall-sized pen. My horse is used to being stalled at night, so that would be plenty of room. While I don’t really see a problem with tying overnight, there is a higher “what if” gut feeling…I would prefer him to be standing untied. I just worry with electric paddocks, and some of the lighter panels…my horse is waaaaaaaaay more likely to break out of his little electric paddock and come to a bad end on a road or something than get tangled up in his halter. I’d need to be satisfied that the panels would contain him at least as well as his halter.