When creating a challenge, you can create a challenge by prompt or book or number.

This request is that when I'm searching for a challenge, sometimes I want to filter it to only show Book challenges, so I'm not also wading through Prompt challenges.

Vaguely similar to searching for a book and being able to limit to a hardcover edition or paperback edition.

I notice the search already has a 'filter' but it only has a Keywords section. Presumably this would just be a second type of filter, perhaps a dropdown or perhaps checkboxes, for the 3 types (and either an All, or just combinations).