Read the HOWTO documentation for more details.
You need to enable grouping in the routers2.conf ( 'group = yes' ) first. Then, you will get one group per directory -- so you'll need to split your .cfg files into separate subdirectories, and have a 'cfgfiles = */*.cfg' or similar to find them.
With the latest beta, you can have multilevel menus with 'multilevel = yes'. In this case, the multilevel is split on the : symbol in the description, so you'll need to define group names for the directories in the [targetnames] section, and add :s to define the group split.
UNIX Systems, ITSS, University of Auckland, NZ
Woe unto them that rise up early in the morning... -- Isaiah 5:11