Well, it’s not a big problem, but current (v4) REST console doesn’t allow to use all backendless v4 “commands”. For example, there is no “count”. And functionality with relation limited too, although I’m not sure, I didn’t looked thoroughly yet.
You’re correct, the “count” operation is not supported by the REST console in the v4 yet. You can still call the function from any other REST tool or client (postman for example).