newsupernova/vendor/magento/module-variable/etc/adminhtml/menu.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Backend:etc/menu.xsd">
    <menu>
        <add id="Magento_Variable::system_variable" title="Custom Variables" translate="title" module="Magento_Variable" sortOrder="20" parent="Magento_Backend::system_other_settings" action="adminhtml/system_variable" resource="Magento_Variable::variable"/>
    </menu>
</config>