We've toyed with this idea before, of at least including the registration in the free-text associated with a log. However we suspect a lot of people Go Flying without necessarily bothering to update the current aircraft such that it reflects the aircraft they're piloting or are a passenger in, so at the moment we leave it to the pilot to add that free-text information if they wish.

Hey,
as a pilot of multiple aircrafts types, it ‌would be very nice to have information about the aircraft used for a specific flight in the LOG (also in the exported KML or GPX file).

I would really love to see this feature in a future release of Skydemon.
K‌eep up the good work and feel free to contact me for any questions ‌concerning this request.