Audiobook storage on external drive

I store all my content on an external drive (Music, movies, books etc).

When I import my books to the Books app a copy is placed in ~/Library folder/com.apple.BKAgentService/Data/Documents/Audiobooks or something similar.

Unlike the other media apps, there is no settings part where I designate where media is kept and therefore I seem to have duplicated content with audiobooks maintained in both the external drive and taking up space on my internal iMac drive.

Is there a solution to this as space is precious on the internal drive ?