If you would like to extend your groups and have your own custom pages/tabs inside your groups, you can do this quite easily now without the need of touching code and digging yourself through BuddyPress loops and functions.
How it works
The plugin adds an option to the BuddyPress Docs plugin to select a tag and display the last post from this tag as a group nav item.
After you have added the tag which should be used, you will find the last post of this tag as link in the group navigation. The nav menu name is the title of the post.
You can find the plugin on GitHub:
Bugs can be reported here: