Marketo Custom Object: Lead <- Parent <- Child relationship
The Email Scripting documentation has the following hint:
"For Marketo custom objects, you can reference second level custom objects with Parent-Child relationship. e.g. Lead <- Parent <- Child"
https://developers.marketo.com/email-scripting/
How do I go about actually creating such a custom object relationship?
If I link the Parent object to the Lead, I am unable to create a link between the Child object and the Parent (does not show up as a linkable object).