This mod will increase the font size of the control groups (1,2,3,4,5,6,7,8,9) rendering them visible and more appealing to your eyes. Especially users with 1920x1080, 4k or higher screen resolutions.
A quick demo:
You can either subscribe to the link above then restart the game. Or directly in the game Intro Menu > Mods: search for ‘Huge Number’ then install. Done