I would like to save a listing, so that reading 12,500+ tags is not neccessary each time I start mp3tag. I searched the help file and forums but can not find if this is already possible
If you want to create a list only to prevent Mp3tag from re-reading the tags, this is not possible. However, you can create an export configuration that writes the content of the fields you want into a plaintext (or HTML, XML, whatever) file.