[2020] Disappearing UI

Usually Tab does that. If that doesn't get you back, try hitting Esc a few times and scroll to zoom out.

Originally posted by bear: I get an issue with the UI if I load one city from another (or re-load). If I exit the game (either to desktop or main menu) and then load the city no problem.

You're doing what's called a 2nd load, which breaks a lot of mods. So having some weird stuff happening is expected. Always restart the game after loading once to avoid this. It's how the game loads things - the 2nd load goes "on top" of the first one without clearing the first load. So everything is running twice (or trying to), which messes with mods and increases your RAM usage.