Add ACF option pages

functions.php

<?php

/**
 * Unique identifier for the theme. Used for the text domain and other stuff.
 *
 * @return string
 */
function theme_key() {
    return 'yourthemeid';
}

/**
 * Add option pages.
 */
add_action('acf/init', function () {
    if (!function_exists('acf_add_options_page')) {
        return;
    }
    acf_add_options_page(array(
        'page_title' => __('Theme Settings', theme_key()),
        'menu_title' => __('Settings', theme_key()),
        'menu_slug' => theme_key() . '-settings',
    ));
    $sub_pages = [
        // [
        //     'page_title' => 'Header Settings',
        //     'menu_title' => 'Header',
        // ],
    ];

    foreach ($sub_pages as $page) {
        acf_add_options_sub_page([
            'page_title' => __($page['page_title'], theme_key()),
            'menu_title' => __($page['menu_title'], theme_key()),
            'parent_slug' => theme_key() . '-settings',
        ]);
    }
});

Update the theme_key(). Add sub-pages as needed.