I'm trying to figure out the best UI for:
1.) Presenting users with a default set of search results (let's say 'toys')
2.) Allowing the user to filter those search results per standard checkboxes (filter by age, brand, etc)
3.) But ALSO allow them to expand the search results into different related categories (for example, I'm on a children's products site and I'm viewing toys, but now I'd like to see toys and school supplies all in the same set of search results).
It doesn't seem intuitive to use checkboxes for both filtering the results (only show me these types of toys or school supplies) as well as expanding the search results (show me toys and school supplies). Does anyone have any examples of sites that do this well or ideas on how to present these options?