qmk-firmware/keyboards/ergodox_ez/keymaps/hacker_dvorak/keycodes/custom_keycodes.c

// Define custom user keycodes:
enum custom_keycodes {
    PLACEHOLDER = SAFE_RANGE,  // Can always be here.
    MY_CUSTOM_MACRO,           // Custom macro example.
    MY_OTHER_MACRO,            // Custom macro example.
    DYNAMIC_MACRO_RANGE        // Should always be the last.
};