Default File Name on Export

Here's what I would like to do:
I would like to be able to define what the default file name will be when I print or export to PDF. So, for example, I have the instrument set up as Soprano Sax, but I want the file name to be as follows: "Filename Tx" because it's a lead sheet for tenor sax but I don't want it transposed up an octave.

Here's what happens:
If I export using the print-then-PDF route, the default file name is "Untitled." (Why?)
I I export using the export function, the default file name is "Filename-Soprano_Saxophone." Too long! No matter what I do to the name of the instrument, MuseScore insists on "Soprano_Saxophone" as the name of the instrument for the file name.

Is there any way for ME to define what the file name should be?