It's working for me. You might want to try a small "s"
My key letter for that search engine is a small "s"
I'm not sure why you're having a problem, as Start page, using the key letter is working for me from the Opera omni search/address bar.
On your question, I don't know the answer, but it's been quite a few updates and no default engines have so far been added, that I'm aware of.