Short answer
HubSpot's KB: Edit record can copy values between properties, on the same record or with associated records. The association must exist before the action, and source and target must be compatible types. If several associated records qualify, the value may come from the most recently updated one, not the primary.
1. The action
Edit record in my demo portal.
2. Keep it current
HubSpot suggests re-enrollment to keep the value updated whenever the source changes.