From there, I wrote a Rust program to generate labels. It drives Labelle with the new batch mode I wrote for it at https://github.com/labelle-org/labelle/pull/72 . The Rust program can take LCC and ISBN and generate the label, or it can take ISBN and do a lookup to the exported data and generate the label from that. Great with the barcode scanner.
The labels themselves encode the ISBN in the QR code. If no ISBN is present, they hold a local barcode number generated by LibraryThing. 4/