Does not exist, but is something that's being considered!
That being said, I recommend doing the following - before revealing the answers, think of the answer in your head. After, reveal the answer, and only choose the answer if you thought of it previously, otherwise choose Skip. This both confirms whether you really know the answer or not (and am not just eliminating choices), but keeps your speed up because you don't need to do fill in the blank.
But yes, it will hopefully be added in the future :)