Marketo was built from the ground up on the idea that all fields should be on the person record. Yes, you can pursue a one-to-many design using Custom Objects but they are difficult to use because they are implemented by way of API calls.
Features that could solve this:
- Add new "List Field" Fields Type that can hold multiple values.
- Support one-to-many with Flow Steps to Add/Remove/Filter items in "List Field" or Custom Objects
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