Hi @alexandro.oliveira , welcome to Auth0!
This approach is valid and documented.
scope and the corresponding requested_scopes is a standard param.
The doc (Accessing Query String Parameters in a Pre-User Registration Action) refers to additional key:value query parameters added to the /authorize request.
For reference, to see what I mean by additional key:value query parameters, please take a look at this topic: Oauth/token request payload custom key/values
Please let me know if we can answer any other questions on this topic!