Sort also by author‘s last name

I have a huge library of books, over 6000, and all of them have the author‘s name in their metadata in the following form: "first name, (middle name), last name". When I import my library into bookshelves the feature "sort by author" sorts all the authors alphabetically by their first name. I prefer your excellent app to many other applications, but many of them have offered this possibility. It would be very helpful if you can provide this choice. Otherwise I would be lost with the task of changing the metadata of all my 6000 books. Many thanks and best regards!