etc/adminhtml/menu.xml
<?xml version="1.0"?>
<!--
/**
* Copyright © 2018 Stämpfli AG. All rights reserved.
* @author marcel.hauri@staempfli.com
*/
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Backend:etc/menu.xsd">
<menu>
<add id="Staempfli_Seo::search_engine_optimization" title="Search Engine Optimization" translate="title" module="Staempfli_Seo" sortOrder="100" parent="Magento_Backend::marketing_seo" action="adminhtml/system_config/edit/section/seo" resource="Staempfli_Seo::seo"/>
</menu>
</config>