WS-FED custom attribute statement questions

I have a ws-fed app that needs a custom profile attribute that is a string array that I’d like to pass in the Custom Attribute Statement in the app settings. When I add the field name, I get an error. Is there a way to do this?

Also, if I wanted to pass back the okta userid, what would the statement for that be (I tried all combinations of user.userid)?

Thanks,

Richard