qmk-dactyl-manuform-a/keyboards/rama/m6_a/keymaps/naut/keymap.c

#include QMK_KEYBOARD_H

// Define Layers
#define _BASE 0
#define _FNX 1

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {

    // Base Layer
    [_BASE] = LAYOUT(
        TO(1), KC_UP, KC_PGDN,
        KC_LEFT, KC_DOWN, KC_RGHT),

    // Fn Layer
    [_FNX] = LAYOUT(
        TO(0), KC_VOLU, KC_MPLY,
        KC_MRWD, KC_VOLD, KC_MFFD)};