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.

local wezterm = require 'wezterm'

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