I realized recently that the default export format for a new session is 16-bit WAV. I always change that when exporting mixes, but it occurred to me I’ve probably used the default a few times when exporting / re-importing.
Is there a way to set to the default format so that my export re-imports will be at 24-bit without my having to change it for each session?
Also, is there a functional difference between exporting / re-importing 24- vs. 32-bit, assuming my session audio file format remains at 32-bit float (the default)?
I just tested this:
I created a custom “Export Format Profile”, then exported using it, then tried exporting the session again (via ^E) and it does indeed pre-load that last export profile used, which is nice of course.
However, in a new session the export profile defaults back to the WAV 16-bit one… Hmm… 
Thus circling back to your original question:
…
You might want to submit a feature request on Mantis about this. Perhaps ‘all’ that needs to be done is the implementation and use of a ‘default export format profile’ line of code in the main config file that Ardour 9 uses. 
-J
Basically with 32bit export you don’t have to worry about clipping and you avoid dithering, it’s the way to go if you’re to going import the file in a session.