Hi @geoff2,
Thanks for reaching out to the Auth0 Community!
Unfortunately, there is no way to create custom claims through the Universal Login HTML code. Instead, you must use a Post-Login Action to append the custom claims to the tokens, as you have found.
Moreover, the data you can get in the Post-Login Action only include the following fields found here.
The fields do not have a way to pass the “Remember Me” option from your Custom Universal Login Page to your Web App.
Please let me know if you have any questions.
Thank you.