Expose the ArcGIS token in scripts

For context, see my earlier question here: https://support.vertigis.com/hc/en-us/community/posts/12564033935762-Get-ArcGIS-request-token

It seems that the token is only available when it is set in a GET or POST parameter, but not in a cookie. I'd like to have a generic way to use the ArcGIS token in an Access Control script, maybe something like request.getToken, or a top-level variable named ‘token’