Here is the link to the forum post of the autoshelf mod.

It’s a simple to install but unfortunately a bit fiddly in my opinion. When you plug the reader in via usb, a symbol appears on the device screen that you can tap to run autoshelf upon usb disconnect. Unfortunately it only works on books that have already been added to the device, so you have to plug your reader in twice. Once to transfer the books and a second time to run autoshelf on the added books.

I also use NickelMenu in which I added a button to run autoshelf without having the USB plugged in. My script works by pretending the USB was plugged in, thereby showing me the usb screen and allowing me to tap the autoshelf symbol and then waiting for around 10-15 seconds before “unplugging” the USB again which causes the autoshelf to execute.