ability to add sub categories in apps

There are some scenarios where there is a need of contextual grouping of pages at more detailed level. Currently, we can different categories and group the pages together as per the functional areas. There is also a need of an option where we can create sub categories within a category for grouping of some pages in a more specified manner. Sometimes, within a category, it can be a long list of pages and these all are related to the category. So, if we can have option of sub categories creation, it would be helpful to organize the pages in an effective and efficient manner.