Having the ability to nest Dropdown menus would be extremely useful for mega menus that are more complex.
E.g. The website I’m currently building has the structure
Colleges
- India
-
- College 1
-
- College 2
-
- College 3
- USA
-
- College 4
-
- College 5
-
- College 6
- UK
-
- College 7
And so on. So being able to provide people the ability to have India, UK, USA also be dropdowns that are dynamically looped through would allow for much more complex Menus to be made. This is especially great for Mobile where you want to show levels of lists instead of just the whole list opening up.