I want to import a Portfolio that's shared with me but I'm unable to find the associated API action for it. (As I want to do it programmatically)
I'm looking for a translation in both Terraform as well as CFN of the specific API action and I can't seem to find it. Anyone an idea?

Terraform does not have a resource for this yet.
CloudFormation allows you to accept a portfolio share through the following resource: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-servicecatalog-acceptedportfolioshare.html