After the update, there is no option for editing the token payload.
Hello,
You’re right—after the update, direct editing of the token payload is no longer supported via the UI. Since JWTs are immutable by design, any changes require generating a new token with the updated payload. Consider using a refresh mechanism or backend logic to issue updated tokens securely.
Best Regards,
Amy Cross
Editing payload is a very nice feature where we can design token information and test before the deploy. Its also helping to fast switching profiles on same resource. 
I recommend using another tool. There is an old version of JWT debugger: jwt.lannysport.net