I'm not quite sure if you're looking for the moderate option for quizzes or for assignments. I think there is potential for confusion as Canvas uses the term "moderate" to mean two slightly different things depending on which tool you're using. Moderating a quiz means giving certain students extra time or attempts, as described in the link that @Chris_Hofer posted. Moderating an assignment means allowing several course teachers to grade the same submission and then choosing which of those grades to post to the student, as described here: How do I add a moderated assignment to be graded by multiple reviewers?
You asked if this is a feature option. It is, and if you don't see the option when creating an assignment then you might need to ask your local Canvas admin to turn it on at account level.