Just a few little things I noticed with my laptop+external screen setup:
1. There is no settings for selecting the screen I want to use
2. Switching to fullscreen breaks mouse integration - the displayed cursor position does not reflect which UI item is hovered
3. Since there is no windowed mode (only windowed borderless mode), I am unable to drag&drop the game window to my primary screen.
Oh, and the reset setting button does not work, nor am I able to disable fullscreen now. I tried restarting the game, but now I am unable to even get past the alpha info screen, since keyboard cannot be used to control the menus.