MT(mod, kc) send kc instead of mod when the key has tapped -> hold · Issue #889 · qmk/qmk_firmware

I've using a MT macro to make a key which send Ctrl when hold, and Space when tapped. And the definition said MT(mod, kc) - is mod (modifier key - MOD_LCTL, MOD_LSFT) when held, and kc when tapped...