I believe that you are correct that you cannot create tablature using BIAB; you can only view tab of RealTracks that came with tab.

You should look into TablEdit. That is a program that is supposed to be able to create tab for any stringed instrument, and some non-stringed instruments! They say you can import a MIDI file. So you could take a melodoy from BIAB, export it to MIDI, and create tab in TablEdit. I have never used it myself -- only saw it on the web.