Hi im using UE4 since 2018 and todays I just created 2 levels (a menu level and game level), but when i open my first level(menu) and close the second in editor, the second just dissapears and only his built data file is there. And yes I save it.
I had an issue similar to this once. Could you provide screenshots of your editor?
Oh Thanks but I restarted the UE4 and now its Ok. It was maybe a small bug.