you can make a filter over fanfiction as follow:
needle => contain needle
~needleA ~needleB => is needleA or needleB
-needle => doesn’t contain needle
char:harry => have character named harry
rated:all => have all ratings (for all use it by default)
pair:harry/hermione => have a pairing of harry with hermione
fav:>1000 => have more than 1000 favorites
published: have been published since 2 years ago
review:>50 => have more than 50 reviews
words:>3000 => have more than 3000 words
updated:>2months => have been updated before 2 months ago
genre:action => is of the action genre
is:complete => is complete
fandom:firefly => is of the firefly universe
is:crossover => is a crossover
lang:english => is in english
sort:fav => will sort by favorites as default