adding subcategories for pretty plugins

is there a quick way of adding sub categories to pretty plugins.

e.g. right now i have pretty plugins configured and customers can sort plugins by levels
silver, gold and platinum. What i'd like to offer my customers is the ability to have another level of refinement. say refine gold level plugins by category "advertizing" , "seo" ,"e-commerce ", "Marketing" etc etc .

please let me know if there's a quick way of doing it.