I am having trouble referencing API Secrets via suitescript using the secret id generated with the new API secrets management feature in 2021.1. How are these resolved in script?

How are you trying to use it? My understanding is that you can only use the secrets with other NS-apis that can consume them. You can never get the actual key/password as a string in your code.

I may be misunderstanding the API secrets but I was hoping to resolve them in my script in the https method for a 3rd party API call. I am able to do this with the addCredentialsField method to create a secret hash that resolves via https.SecureString (as seen in Marty Zigman's article https://blog.prolecto.com/2014/09/17/how-to-use-netsuites-nlapirequesturlwithcredentials-api/). It seemed as though the new feature would allow me to do this in the same way, but with better management. The code sample in the help docs Account Administration > Authentication > Secrets Management > Code Sample shows how to reference a secret by using its script ID, but it doesn't make any sense to me.