Madsy,
Thanks for the added information. I now have a clearer picture in mind as to what you want to achieve.
Using BIAB as music-scoring software is limited. The program is designed to create leadsheets mostly (melody line and chord symbols) and when doing this, it does a great job.
For notating piano scores, MuseScore is much better software. I use it regularly. It's free and can be found at the link below. It will easily do the scoring and the transposing you require.
https://musescore.org/There are a number of Youtube clips on how to use MuseScore. Once you get the hang of it, it's very straightforward.
It's also possible to export a MuseScore file as XML or MIDI and then load it into BIAB.
As always, when installing Freeware or Open Source programs, choose the 'manual' install option and de-select any third party software such as search engines or antivirus trial software that sometimes accompany freeware.
Regards,
Noel