One to Many Relation for Segment Custom Fields
Right now, you're only able to store a one-to-one relationship with custom fields in Segment...
Use Case
We have a website for realtors and we want to track each property the user is interested in. When they opt-in or take an action on a page, we want to identify them and store the value with their lead.
At the moment, we'd have to create a new list each time for each page and it can quickly add up.
Rather if the value was stored in a one to many custom field, we could make a smart segment on the fly and start a journey on the fly!
ie. Interested in Property: 129 Westfield, 190 Chester Drive
Smart Segment --> Custom Field: Interested in Property = 190 Chester Drive
Hope that makes sense.