The structural files in our packaged game systems are not accessible to users, which means that new attributes can't be created and new tabs can't be created.
I think you'd have to start from the skeleton in the authoring kit. Especially since Buck Rodgers isn't a d20 game, it's a variant of 2ed. You've voted for "d20 system mechanics" in the "What Games Should HL Support" thread in the general discussion forum, right? - I'm afraid that's what you really need for this sort of thing, and I'm sorry that we haven't had the time to create it.
The attributes in a game system are generally stored in a file called "thing_attributes.dat" - you can open that file in your copy of the skeleton files and edit the properties of the sample attribute.
The "Attributes" link here discusses how the attributes were modified when the savage worlds files were created using the authoring kit:
http://hlkitwiki.wolflair.com/index....s_Walk-Through