Hi. Looks like I found the first bug of 2019.
I was creating a new level. I was intending to press the scroll-up button. I misclicked and pressed the close button and boom! The editor's gone with my progress gone, with no warning message either.
So what I'm saying is: The pop-up message needs to appear every time I press the close button on the editor, including when I'm making a new level. ATM it only comes up after the level is saved into a file. I hope this makes sense. Thanks.