On a 2013 on premise, I need to deal with a LOB system via SOAP or REST calls.
But how can I pass these as variables :
the following calls have to use basic auth with a predefined login and the token as password.
token (digest) is not being used in place of password.
you have to provide user credentials to authenticate against remote host (either manually typed in or from stred credentials).
request token (digest) is being sent as an additional header attribute.
see chapter 'How to execute a POST request' in linked blog.
then I affraid nintex workflow action(s) doesn't support this kind of authentication.
maybe if it would be an option for you to move functionality to forms, web request form control seems to support basic authentication