Add new format?

In addition to my ebooks, I have a large library of paper books.

Is there some way I can add something like "Paperbook" to my list of possible formats in Calibre? That way I can search and/or describe all of my books in one place.

I understand that I can add paper books as -no-format- but I'd like to be able to conspicuously flag these books as being in my paper library. Using tags is just not obvious enough.

I realize this will probably involve editing some config file deep in the guts of Calibre. Can it be done?


Thanks!