I've written to the board help/suggestion contact email, asking for a separate "Genre" for foreign language...adding a new genre for foreign language would not only make finding them about a zillion times easier, but it would also make a convenient place for those of us listing foreign books to place them.  Subcategories could be added for particular languages or adult/children too, if they so choose.

This was the reply:

The database is compiled elswhere, and we can't add or create new
genres, since the database won't recognize them.  It is best to search for
the language you are interested in one of the subgenres under World
Literature, or by searching for the language using the keyword search.

You are right, Spanish is by far the most popular foreign-langauge
searched for here, and because of this we have made a link to Libros en
Espanol on the Browse by Genre tab under Search in the top menu, to pull
these books together in one easy search for members seeking