[kiwidude]

I don't understand. There is no concept of a "default shelf" in this plugin. The menu items for adding to a shelf or syncing from a shelf always refer to a specific shelf name. So if you want books on your "to-read" shelf then you use "Add to shelf" -> "to-read" etc.

What are you doing that is so different?

EDIT: There is one scenario that perhaps you are hitting. Are you perhaps trying to add to a non-exclusive shelf, without having it on your exclusive shelves as well? IIRC it is a limitation of Goodreads that every book must exist on one of your exclusive shelves. And if you haven't put it on one of your Goodreads exclusive shelves, then the Goodreads website will put it on your read shelf as a default. Is that the behaviour you see?

In which case the solution is simple - add the book to your to-read shelf first then as well to your custom shelf. If you don't want it on both, you have to make your custom shelf exclusive.

I don't use non-exclusive shelves myself (I'm really only interested in the "read" shelf in my usage) but I am aware of others asking for the ability to add to multiple shelves at once. The issue is that there is a lot of complexity behind that which requires a major change to the plugin, which I don'#t have time for at the moment.