[capink]

Your understanding of the concept of book_vars is fine. The problem is with your understanding of Conditions. The condition does not work per book, it works per action. So if the condition is True, the action will run for all selected books. If the condition is False the action will not run at all.

Since the condition does not iterate over all books, It only fetches one metadata object (active index in case of multiple selections). This explains what happened when you selected only one. (conditions in case of multiple selections are meant to be used for general things like selection_count, connected_device_name, current_library_name .... etc)

I am not sure whether the above is explained clearly. Anyway, to achieve what you want, the solution is to store the ids for books that should be processed in step 2. Attached below is a zip with a modified chain that should achieve this. It uses the scopes feature.