qmk-firmware/keyboard/hid_liber/keymap_custom.h

// hid_liber custom
// ANSI layout with FN key instead of APP button
// Layer 1 has mediakeys on the nav cluster and keypad numbers for alt-codes

static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
/* Layer 0: Default ANSI
 *
 * ,---.   ,---------------. ,---------------. ,---------------. ,-----------.
 * |Esc|   |F1 |F2 |F3 |F4 | |F5 |F6 |F7 |F8 | |F9 |F10|F11|F12| |PrS|ScL|Pau|
 * `---'   `---------------' `---------------' `---------------' `-----------'
 * ,-----------------------------------------------------------. ,-----------.
 * |~  |  1|  2|  3|  4|  5|  6|  7|  8|  9|  0|  -|  =|Backsp | |Ins|Hom|PgU|
 * |-----------------------------------------------------------| |-----------|
 * |Tab  |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|    \| |Del|End|PgD|
 * |-----------------------------------------------------------| `-----------'
 * |Caps  |  A|  S|  D|  F|  G|  H|  J|  K|  L|  ;|  '|Return  |              
 * |-----------------------------------------------------------|     ,---.    
 * |Shft|iso|  Z|  X|  C|  V|  B|  N|  M|  ,|  .|  /|Shift     |     |Up |    
 * |-----------------------------------------------------------| ,-----------.
 * |Ctl|Gui|Alt|          Space                |Alt|Gui|FN1|Ctl| |Lef|Dow|Rig|
 * `-----------------------------------------------------------' `-----------'
 */

  KEYMAP(\
      ESC,   F1,   F2,   F3,   F4,   F5,   F6,   F7,   F8,   F9,  F10,  F11,  F12,       PSCR, SLCK,  BRK, \
      GRV,    1,    2,    3,    4,    5,    6,    7,    8,    9,    0, MINS,  EQL, BSPC,  INS, HOME, PGUP, \
      TAB,    Q,    W,    E,    R,    T,    Y,    U,    I,    O,    P, LBRC, RBRC, BSLS,  DEL,  END, PGDN, \
     CAPS,    A,    S,    D,    F,    G,    H,    J,    K,    L, SCLN, QUOT,        ENT,                   \
     LSFT, NUBS,    Z,    X,    C,    V,    B,    N,    M, COMM,  DOT, SLSH,       RSFT,         UP,       \
     LCTL, LGUI, LALT,              SPC,                         RALT, RGUI,  FN1, RCTL, LEFT, DOWN, RGHT),

/* 
 * Layer 1: Media Keys
 *          Keypad numbers instead of normal numbers
 *
 * ,---.   ,---------------. ,---------------. ,---------------. ,-----------.
 * |Esc|   |F1 |F2 |F3 |F4 | |F5 |F6 |F7 |F8 | |F9 |F10|F11|F12| |PrS|ScL|Pau|
 * `---'   `---------------' `---------------' `---------------' `-----------'
 * ,-----------------------------------------------------------. ,-----------.
 * |~  |KP1|KP2|KP3|KP4|KP5|KP6|KP7|KP8|KP9|KP0|  -|  =|Backsp | |Ins|Med|Vl+|
 * |-----------------------------------------------------------| |-----------|
 * |Tab  |  Q|  W|  E|  R|  T|  Y|  U|  I|  O|  P|  [|  ]|    \| |Del|Mut|Vl-|
 * |-----------------------------------------------------------| `-----------'
 * |Caps  |  A|  S|  D|  F|  G|  H|  J|  K|  L|  ;|  '|Return  |              
 * |-----------------------------------------------------------|     ,---.    
 * |Shft|iso|  Z|  X|  C|  V|  B|  N|  M|  ,|  .|  /|Shift     |     |Ply|    
 * |-----------------------------------------------------------| ,-----------.
 * |Ctl|Gui|Alt|          Space                |Alt|Gui|FN1|Ctl| |Prv|Stp|Nxt|
 * `-----------------------------------------------------------' `-----------'
 */

 KEYMAP(\
     TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS,       TRNS, TRNS, TRNS, \
     TRNS,   P1,   P2,   P3,   P4,   P5,   P6,   P7,   P8,   P9,   P0, TRNS, TRNS, TRNS, TRNS, MSEL, VOLU, \
     TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, MUTE, VOLD, \
     TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS,       TRNS,                   \
     TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS, TRNS,       TRNS,       MPLY,       \
     TRNS, TRNS, TRNS,                   TRNS,                   TRNS, TRNS,  FN1, TRNS, MPRV, MSTP, MNXT),

};

static const uint16_t PROGMEM fn_actions[] = {
	[1] = ACTION_LAYER_MOMENTARY(1),		// activate layer 1 when FN1 pressed
};