Setting up per user JWT claim Named Credential

Question

I'm trying to setup a per-user JWT claim as per the documentation here the issue is it specifies

Subject of the token (the user).

The subject is a string when the identity type is named principal, and it’s a formula when the identity type is per user.

The issue I have is what is actually accessible from this?

I have tried the below:

$User.FederationIdentifier

{!User.FederationIdentifier}

And it doesn't seem to merge them into the claim am I missing something?

Answer 1

Documentation is not clear.

After a few tries, it worked with {!$User.FederationIdentifier}