Feature request: Primary display from desktop mode should be the display in game mode

[TriVoxel]

I set my primary monitor expecting the game mode to use it. However, game mode defaults to the right-most port on my graphics card. This is less than ideal, especially considering my primary monitor is a DisplayPort monitor, and thus can't be physically positioned any higher on my GPU. Furthermore, editing a config file is not very user friendly. The expected behaviour is for the primary display defined in the desktop mode to be the primary display in game mode.