Hi Theresa! This is an interesting use case. I'm happy to share some thoughts here.
First, I think these are 2 separate use cases:
1. Set up the email preference center and subscription groups.
2. Set up an IAM that subscribes users to the newsletter subscription groups.
For #2, you may be successful with the trigger "interact with campaign" --> Clicks IAM button 1. And then you'll have to set up a webhook to add the user into the Subscription Group.
I'm curious also, so I may do some testing on this one from my end! Let me know if you have any questions in the meantime.
