Per chance I discovered that several of the volumes in Shcaff's edition of the Church Fathers are Bible Indexed! This means I can have Logos scan them in a Commentary section of a Passage Guide. For the moment I have tagged them as part of a subtype of commentaries. (See below.)
I wonder for what other books Logos built Bible indexes, that may not be obvious? This is one of the reasons why I wish we could sort the library display by how a book is Logos indexed. I would think this is an easy feature to implement.
P.S. I am still thinking about how to subdivide my commentaries. These will probably move to another subdivision later.