Hi Charan!
Mendix only allows two levels of menu, and you cannot have a sub-menu that is level 3.
Example of allowed menu:
Categories → List of Categories
Example of not allowed menu:
Categories → List of Categories → List of Subcategories for each Category
I’m using version 9.24.4 and I can use 3 levels of menu. However, in my case, I want to use 4. How can I solve this problem? I don't know how to solve it either. Did you find it?