Well first of all, why are you editing official maps???? LOL jk.
I know that whenever I used edit mode and selected a cube, the red square would remain on the selected area. If I didn't select any cubes, the white square followed my mouse and when I move my mouse like you do in your video it does the same thing with the white square not remaining centered on the screen. Idk if it is a bug or not though, maybe it was not intended to be centered all the time.
I know that whenever I used edit mode and selected a cube, the red square would remain on the selected area. If I didn't select any cubes, the white square followed my mouse and when I move my mouse like you do in your video it does the same thing with the white square not remaining centered on the screen. Idk if it is a bug or not though, maybe it was not intended to be centered all the time.