In Turn Coat, Harry visits Ebenezar McCoy‘s office. During this visit, Harry reads his grandfather’s journal and McCoy tells him that Harry might want to document his knowledge in a journal. McCoy also implies that this is traditional, as his master and his master’s master etc. til Merlin have done so.
I think the Dresden Files are these “journals”.
I also think it would be hilarious if Bob wrote them for Harry.  I have no proof of this besides the fact that Bob is one of the few characters that Harry tells the “whole story” to.

Ps. I am new to this forum. I apologize if this theory is already out there.