Question on Category Listings

My sports betting blog http://sportsinfo.pinnaclesports.com uses a Fold Category List plug-in taken from http://www.webspaceworks.com/ which enables the creation of sub-categories. However, you cannot tell that these sub-categories exist until you click on the parent. Ideally I would like the categories to function like the Windows folder hierarchy with +/- symbols to let you know whether there are further levels.

Any ideas?
I will be grateful for any help but please be aware I am not a techie.