How to register options pages in Advanced Custom Fields for WordPress (ACF). See https://www.awesomeacf.com/snippets/register-options-page/ for more details.

register-acf-options-page.php

<?php

// register a top-level options page
if ( function_exists( 'acf_add_options_page' ) ) {
	acf_add_options_page( [
		'page_title' => 'My Options Page',
		'menu_title' => 'My Options Page',
		'menu_slug' => 'my-options-page',
		'capability' => 'edit_posts',
		'parent_slug' => '',
		'position' => 3,
		'icon_url' => false,
		'redirect' => false,
		'post_id' => 'options',
		'autoload' => false,
		'update_button' => 'Update',
	] );
}

register-acf-options-sub-pages.php

<?php

// register two sub-level options pages
if ( function_exists( 'acf_add_options_page' ) ) {
	$parent = acf_add_options_page( [ …top level options here… ] );

	acf_add_options_sub_page( [
		'page_title' => 'My Sub Options Page',
		'menu_title' => 'My Sub Options Page',
		'parent_slug' => $parent['menu_slug'],
	] );

	acf_add_options_sub_page( [
		'page_title' => 'My Second Sub Options Page',
		'menu_title' => 'My Second Sub Options Page',
		'parent_slug' => $parent['menu_slug'],
	] );
}