How to pass back custom user attributes in the SAML attributes payload?

Is at all possible to return custom attributes in the SAML attributes payload on authentication success.

I am able to map over the givenName and surname since those are our of the box but let’s say I added a custom user attribute of security question and security answer.

While I can retrieve these from a user using OpenConnect and OAuth flows I cannot get them to map to SAML attributes.

I have created a client scope on the realm for securityQuestion1:

With a client mapper of:

And on my client in this realm I have added the scope to the client details:

However, even after doing this all I receive in the attributes is the first name and last name.

Is there a way to expose the custom field? Am I doing something incorrectly?