It would be good if Export New's opening of the config file for editing uses the associated app (as does Edit) rather than Notepad regardless, as currently.
I've added this with the current Development Build.
Kind regards,
Florian
And afterwards it would be nice to have the text output displayed in the same editor application like in the new or change section.
DD.20071109.2258.CET
Detlev, do you mean the export result?
Yes. It would come handy to use the same editor application in all three states 'new, edit, view output' in the case of producing pure textual output (.txt,.bat, *.mte, ... or something else).
On the other hand a html output in a *.html file should be displayed with the appropriate html browser application (this works as expected).
DD.20071110.1200.CET
Just correct your file type associations if you like the text output to be displayed in the editor you're using for editing export configurations.
Kind regards,
Florian
Confirmed on V2.39e. Goodbye Notepad, hello Textpad 
Many thanks, Florian.
PS People may like to know that a great advantage of Textpad here is that it can be set to reuse the current document window for successive Mp3tag opening's of the same file, greatly reducing desktop litter.