OpenStreetMap community

EDIT: Thank you for all the method to do a research. I'll try them all when I'll have a bit of time.

When I move in a new place, I always look for a map of libraries and for the closest public bookcases.

According to wikipedia

A public bookcase (also known as a free library or book swap or street library or sidewalk library) is a cabinet which may be freely and anonymously used for the exchange and storage of books without the administrative rigor associated with formal libraries. When in public places these cabinets are of a robust and weatherproof design which are available at all times. However, cabinets installed in public or commercial buildings may be simple, unmodified book-shelves and may only be available during certain periods.

At my current place I couldn't find a map of bookcases and I didn't find one walking around my home. Fortunately there is OSM and the very helpful site www.boites-a-livres.fr. The site maps out every french public bookcase using OSM and gives very clear information about how to find them on OSM, even for beginner user like me.

In OSM, public bookcases are represented by a amenity key and a public_bookcase value. They can be either node or area element.

However, if I search for "public_bookcase" in openstreetmap.org search bar, I don't get the result I want. How can define in my research keys and values?

Thank you for your help.