How can I redirect user directly to Sign Up page - closer

If you are using the Classic ULP and not the New ULP (Universal Login Page), then the approach is different. And since you mention Tab I assume you’re using the Classic ULP, because the New one doesn’t have tabs. (The linked docs refers to the New ULP.)

Whether to use Classic or New ULP is chosen in the Auth0 Dashboard > Universal Login.

For the Classic ULP, this would be the approach:

You would add that parameter mentioned in option B in the authorization request towards Auth0. Where exactly depends on the SDK you’re using (Auth0.js, auth-spa-js, something else?)