Xjyuk

I am trying to add a menu for my module in admin panel. I want to add it like Grand Parent > Parent > Child structure.
I have used below code in my menu.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Backend:etc/menu.xsd">
 <menu>
 <add id="Vendor_Module::jsutariya" title="Grand Parent" module="Vendor_Module" sortOrder="100" resource="Vendor_Module::jsutariya" />
 <add id="Vendor_Module::listgallery" title="Parent" module="Vendor_Module" sortOrder="10" resource="Vendor_Module::listgallery" parent="Vendor_Module::jsutariya" />
 <add id="Vendor_Module::settings" title="Child" module="Vendor_Module"
 sortOrder="40" action="adminhtml/system_config/edit/section/list_gallery"
 resource="Vendor_Module::settings" parent="Vendor_Module::listgallery"/>
 </menu>
</config>

But I can only see Grand parent and child menus. Please check below screenshot.

Honestly, I didn't give the proper answer to your question. But found a way to show the parent menu. Actually, Magento is hiding First "parent" menu via CSS. So you need to add another parent menu and will display your previous parent menu.
Here is my code:

 <?xml version="1.0"?> <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Backend:etc/menu.xsd">
 <menu>
 <add id="Vendor_Module::jsutariya" title="Grand Parent" module="Vendor_Module" sortOrder="100" resource="Vendor_Module::jsutariya" />
 <add id="Vendor_Module::jsutariya_listgallery" title="Parent" module="Vendor_Module" sortOrder="10" resource="Vendor_Module::listgallery" parent="Vendor_Module::jsutariya" />
 <add id="Vendor_Module::jsutariya_settings" title="Child" module="Vendor_Module"
 sortOrder="40" action="adminhtml/system_config/edit/section/list_gallery"
 resource="Vendor_Module::settings" parent="Vendor_Module::jsutariya_listgallery"/>
 <add id="Vendor_Module::jsutariya_listgallery1" title="Another Parent" module="Vendor_Module" sortOrder="20" resource="Vendor_Module::listgallery" parent="Vendor_Module::jsutariya" />
 </menu> 
</config>

The main culprit is the following CSS and I don't know why its added in the first place by Magento

.admin__menu .level-0 > .submenu > ul > .level-1:only-of-type > .submenu-group-title 
 display: none;

You have to need change _menu.less for fix the child menu issue actually Admin Navigation Menu labels hide in css.

You can change below _menu.less file path and comment code which is already display:none.

File path:

magento/vendor/magento/theme-adminhtml-backend/Magento_Backend/web/css/source/module/_menu.less

// This part hides Submenu Group Titles only for menus with single groups.
 /*.submenu .column:only-of-type .submenu-group-title,
 .level-0 > .submenu > ul > .level-1:only-of-type > .submenu-group-title 
 display: none;
 */

For more Details refer below links:

https://github.com/magento/magento2/issues/13707

https://github.com/magento/magento2/commit/d91e96b529e70dcec55d3b5336b471791dc42d54