I see now the error of my ways, it is simply one of my misunderstanding of the program's nomenclature. In the File menu, the choices in the Save group are 'Save Selected Files', 'Save Selected (File) as...' and 'Save All Files'. I assumed that the 'Save Selected (File) as...' choice to mean that a single, highlighted track - a portion of a single file- would be copied out into it's own file. (Parentheses are mine). Rather, it is really is a re-naming tool for the whole file which is currently selected in the file management area, and not a portion of a track in the map viewing area.
That all said, I still would like to know a best practice for copying a selected/highlighted track or subset of tracks to a separate file. Any ideas are appreciated.