This is the easy solution when you open ASTRONEER you get this windows
click on ASTRONEER Windowed (like in photo) and than click on PLAY
However if Solution 1 is not working for you can try Solution 2.
Solution (2 (This solution is a bit harder to do)
Open your File Explorer copy this "C:\Users\username\AppData\Local\Astro\Saved\Config\WindowsNoEditor" and past it in your search bar in File Explorer.
Make sure you type your own "