Dropdown Menus in Category widget

Hi

I have a sidebar widget at http://www.softydownloads.com that shows all of the categories and sub-categories for any and all of my listings in Directory theme. However there are so many categories and sub-categories that I need to have a drop down menus or pop-out menu for all of the sub-categories. I’ve tried several different widgets and plug-ins but have had no luck whatsoever.

Does anyone have an easy solution?

Thanks in advance