In many many Gnus screenshots, I see this kind of presentation for the Group buffer:
[groupname1 -- 3]
2: subgroupname1
1: subgroupname2
[groupname2 -- 6]
6: subgroupname1
0: subgroupname2
(ex: http://zarb.org/~gc/img/gnus-screenshot-1.png or http://ostatic.com/files/images/Gnus-%5B2%5D.jpg)
I want to set this up but I do not know how or where to search. Do you have any clue how to reach this result ?