I keep clicking customize, seeing that the options are already how I want them, then look for a back button, don't see one, hit ESC and accidentally go to the main menu. Obviously this is my fault for hitting ESC, but it'd still nice to have a back button to prevent this from happening to me and other dunces like me.

I don't have control over that and additionally even with esc the settings are remembered

When I press ESC, it takes me back to the main game screen, the one with the minecraft logo. So when you hit ESC, it doesn't remember the settings, because it's out of the world creation screen (at least for me).

When I select a profile (e.g. rarecities), it takes me back to the new world settings screen, sorry if I wasn't clear before. Couldn't you add a back button that just takes you back to the world settings screen? Like it does when you select one of the profiles?