Nop

Causes the key press to have no effect; it behaves as though those keys were not pressed.

If instead of this you want the key presses to pass through to the terminal, look at DisableDefaultAssignment.

config.keys = {
  -- Turn off any side effects from pressing CMD-m
  { key = 'm', mods = 'CMD', action = wezterm.action.Nop },
}