I get a lot of questions on how to add more menutabs to the bbMenu. To be short: you can't. This feature will be supported in the next version of bbMenu.
Since I am not a bad guy (and the next release can take a while), I've written a small plugin so you can add menu tabs. It is experimental, so read the read me text before using it!
You can download it here:
http://www.bbportal.org/bb-downloads/addmenutab1.0.zip
More info: http://www.bbportal.org