I already thought of 2 text entries, one for "Concert score", one for "Transposed Score", which you could fill-in as you like in the File Info window, and that Finale would use in the corresponding display.
AFAIK, the "Score" entry will display in both the Concert and the Transposed score. My suggestion is to have 2 separate entries, one for each display.
I know that a workaround would be to make a copy of the score (one would display in concert key, one transposed), and change the name of the score accordingly, but I could use a solution that would only require 1 file.
Since I write sometimes for musical theater, I tend to create a "Working Score" as my main Finale document to contain the rehearsal piano staves as well as all the vocals and instrumentalists. I then create a Conductor score without the rehearsal piano as one of my "Parts." I generally keep the working score in concert and transpose the conductor's score.