As the title suggests.
So, I was going to make this suggestion because I thought something about the game looked off in higher resolutions, but then I came to the conclusion that there's hardly a difference in the way the UI looks in the resolutions I tested this at (1366x768 and 1920x1080, respectively)
The HUD is just sized up to fit the resolution. But for those who want to change that anyway, I think a slider that lets you adjust the scale of the UI would be a good addition