First, it would be nice to be able to define a boolean predicate right at the root, when calling .where:

Second, it would help with consistency of future syntax (e.g. HSEARCH-4499) if the definition of a boolean predicate with a lambda was written f.bool().with( <lambda > ) instead of f.bool( <lambda > ). And it would also be nice syntactic sugar, because one would be able to chain lambdas: f.bool().with( b -> complexPredicate1( b, searchParams ) ).with( b -> complexPredicate2( b, searchParams ) )