Do you want calibre to open the Flight Simulator files or just store them? If you just want to store it, you can just drop a bgl file on calibre and it will add it to your library. You could then edit the metadata to add information that you want to see. If you want calibre to be able to open them, that is not likely to happen. People have already been doing this with audio and other file formats.
BTW, this discussion would best to have been done in the calibre forum.
|