QMK RGB Toggle Layer

#define RGB_HOLD_LIMIT 400  //hold for less than 400ms to toggle RGB

enum custom_keycodes {
    RGB_MACRO = SAFE_RANGE,  //custom keycode, name it what you want
}

uint16_t rgb_hold_timer = 0;  //timer variable

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
    switch (keycode) {
        case RGB_MACRO:
            if (record->event.pressed) {        //when RGB_MACRO is pressed
                rgb_hold_timer = timer_read();  //  mark the time it was pressed
                layer_on(layer);                //  go to (layer)
            } else {                            //when RGB_MACRO is released
                layer_off(layer);               //  leave (layer)
                if (timer_elapsed(rgb_hold_timer) < RGB_HOLD_LIMIT)
                    tap_code16(RGB_TOG);        //  toggle RGB if held less than RGB_HOLD_LIMIT ms
            }
            break;
        }
    return true;
}