Buy a window cage so the cat can be "outside". We just open the window and ours enjoys watching birdie videos.
When we are driving we have a 6' red leash on the cat harness so we know where he is located. You could leave it on 24/7.
Our cat does everything he can to get out so we are careful. He often waits for me at the bottom RV step. Had to pick him up, etc. But recently I grab his tail and direct him up the steps - works great. Apparently this annoys him - when he now sees me through the screen he heads up the steps - Cat getting trained - I hope.
Our cat locater doesn't work very well so we cannot depend upon it. He has a collar and harness full time. I don't think a cat will ever fully adapt to a leash but he's adapted better than 3 years ago.
Expect to spend several years training your cat if not a lifetime!
