qmk-dactyl-manuform-a/keyboards/4by3/keymaps/funcpad_horizontal/keymap.c

#include QMK_KEYBOARD_H

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
	[0] = LAYOUT_horizontal(
		KC_F1   , KC_F2   , KC_F3   , KC_F4   ,
		KC_F5   , KC_F6   , KC_F7   , KC_F8   ,
		KC_F9   , KC_F10  , KC_F11  , KC_F12
    )
};