Thanks so much for this plug-in and for all the others of yours that I use
I'd really like to be able to add to Goodreads my bought from and bought date columns from Calibre. I believe that the api calls "Add to books owned" and "Update an owned book" cover this with purchase date and purchase location being what I would like to sync.
My "bought from" custom column is currently set as comma separated text but could be any type of text field, the "date bought" custom column is just a date field.
Thanks for looking at this suggestion!