start menu items categories

Hello: I've been using openSUSE with KDE3 for several years. Recently I installed trinity (last stable) on openSUSE 13.1. I am very satisfied with it so far. The only thing I miss know is how start menu items are organized. In openSUSE they are organized into submenus in 2 or 3 levels (eg System/Archiving/*, System/Desktop/* etc). Unfortunately trinity doesn't have this leveling, most programs are put under one main menu item. Eg the program lists in System menu almost fills my whole screen. Which files do I have to modify to have openSUSE type menu categories? Is it enough to adjust a file in /etc/xdg/menus or do I have to modify every single .desktop files belonging to the given applications, or something else? Thanks, Istvan