[WordPress] WordPress Admin Menu: Re-ordering Submenu Items

00-reorder-submenu-items.php

<?php
add_action('custom_menu_order', __NAMESPACE__.'\\acmeReorderSubmenuItems);
/**
 * Reorders the menu by placing the second item before the first item.
 */
function acmeReorderSubmenuItems()
{
    global $submenu;
    $newSubmenu = [];
    foreach ($submenu as $menuName => $menuItems) {
        if ('acme-api-tools' === $menuName) {
            $newSubmenu[0] = $menuItems[1];
            $newSubmenu[1] = $menuItems[0];
            $submenu['acme-api-tools'] = $newSubmenu;
            break;
        }
    }
}