On my Acer I can save presets as 3 Game Modes OR do:

  any button
  right x4-7 (depending on previous mode)
  enter x2
  down
  enter
  left/right (brightness)
  exit
  down
  enter
  left/right (contrast)
  exit x3

Basically there are only 3 brightness modes on $850 monitor with 400cd/m2 range. Thanks to some fucking idiot who thought that a pair of knobs would look too old.