qmk_firmware/keyboards/keebio/bamfk4/keymaps/via/keymap.c

#include QMK_KEYBOARD_H

// Defines names for use in layer keycodes and the keymap
enum layer_names {
    _MAIN,
};

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
    [_MAIN] = LAYOUT(
        KC_A,
        KC_B,
        KC_C,
        KC_D
    )
};