Please add search, as it would reduce duplicate topics.
There already is a search option in the header. If you use Chrome (and possible other Chromium-based browsers), you can also start writing the forum URL and press Tab to search. You are also shown if any topic like the one you are creating has already been created before while creating new topics.
(And this is not the Scratch forum.)
There is already a search option, look at the magnifying glass next to "Explore" on the right.