qmk_firmware/users/zer09/zer09.h

#ifndef USERSPACE
#define USERSPACE

#include "quantum.h"

enum custom_keycodes { CK_SAFE = SAFE_RANGE, RGUP, RGDWN, NEWPLACEHOLDER };

#define _______ KC_TRNS
#define KC_RGUP RGUP
#define KC_RGDWN RGDWN

#define _BL 0 // The base layer
#define _UL 1 // The up layer
#define _DL 2 // The down layer
#define _VL 3 // The shifted up layer
#define _AL 4 // The assorted layer

#endif