I did let Calibre load the books using the "Config this device" settings you see in the attachment. I'm using a USB connection to the PW6. The books are placed exactly where the config asks them to. Into the "documents/Downloads' folder. I'm not sure what json file you are referring to. I'm not that tech savvy.
https://www.mobileread.com/forums/at...1&d=1736888454