Definitely nice to be able to search by difficulty via Primary Order. But... it only lets you search by "easiest" or "hardest".
A more customized search field for difficulty would let you
search for a
specific difficulty level, such as "intermediate". So I'm moving this to feature requests, as this idea is not yet fully realized.
In my efforts to sort through reports in the forums I actually ran across a request for this feature several times, but usually moved it to "completed features", as you can do what MrA said.
But then I read this report and it dawned on me that you can't yet search for a specific difficulty level.