Add dropdown to CMS menu-items

Hi I hope somebody can help me with my problem.
The problem is I have a CMS for menu-items but I want to add
a dropdown menu-item, like what you can do with Wordpress.
I know that you can put a collectionlist into a dropdown element
but that’s not what I mean. I mean that you can manage the whole menu
in a CMS that gives you the possibility to add menu-items and dropdowns.
Is there a way to do this?

Thanks for help,

Here is my public share link: LINK
(how to access public share link)