newsupernova/app/code/Smartwave/Megamenu/etc/adminhtml/menu.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../Magento/Backend/etc/menu.xsd">
    <menu>
        <add id="Smartwave_Megamenu::megamenu" title="Mega Menu" module="Smartwave_Megamenu" sortOrder="505" parent="Smartwave_Core::sw_all" resource="Smartwave_Core::all"/>
        <add id="Smartwave_Megamenu::configration" title="Configuration" module="Smartwave_Megamenu" sortOrder="10" parent="Smartwave_Megamenu::megamenu" action="adminhtml/system_config/edit/section/sw_megamenu" resource="Smartwave_Megamenu::config_megamenu"/>
    </menu>
</config>