qmk_firmware/quantum/keycode_legacy.h

#pragma once

// clang-format off

// These keycode names have been deprecated

#define KC_BSPACE         KC_BACKSPACE
#define KC_BSLASH         KC_BACKSLASH
#define KC_SCOLON         KC_SEMICOLON
#define KC_PSCREEN        KC_PRINT_SCREEN
#define KC_PGDOWN         KC_PAGE_DOWN

#define KC_LCTRL          KC_LEFT_CTRL
#define KC_LSHIFT         KC_LEFT_SHIFT
#define KC_RCTRL          KC_RIGHT_CTRL
#define KC_RSHIFT         KC_RIGHT_SHIFT

#define KC_SLCK KC_SCROLL_LOCK
#define KC_NLCK KC_NUM_LOCK