I set up Calibre to add my books to collections when I sent them to my eReader (Kobo Aura H20); not a single book went into a collection. Most of the collections were already on the reader, but empty due to transferring from from an old eReader to this one, before I knew that was possible. Some would've been new collections added to the list.
I've attached an image of the setup... is something missing, or are there more steps required than than configuring the plugin?
Calibre is version 3.29 for Mac, up to date as of today's post.