How to add a discoverable audiobooks directory?

[solus2sail]

I have a number of audiobooks and want to access them easily.
I have the Audible app, but many of my books were not bought via Amazon.
I'm wondering if there's a specific directory I can load them all into or can I create a discoverable audiobooks folder?
There's a folder for podcasts but not one for audiobooks.

 

[jtfwTX]

I don't have audible but for all my downloaded audiobooks, I store them in a folder called "audiobooks" in my downloads folder.