It would be useful to be able to define an individual aircraft by make, model and S/N. Tail numbers can change.
I work for a company that has retained certain N-numbers throught the years because of the historical significance of the numbers to the company. One of them has been used on at least 5 different aircraft, once on the same make and model. Also, in the process of changing aircraft, we re-registered the trade-ins with slightly different numbers shortly before selling or trading them. Makes keeping track of the actual airframes very difficult.
As far as I can tell, this currently isn't possible in Logbook Pro. In the works for future versions?