In addition to establishing the primary link between the user table and the portal table, it's necessary to generate a different linked record field that establishes a connection between the two tables. This field will serve as a repository for the portal user responsible for the most recent modification to the record. After setting this linked record field in Airtable, set it up in your portal. Go to:
Portal Tables
Click on one of the tables
Audit Trail section
Turn on the Enable audit trail for this linked records field toggle
Click on the dropdown and select the linked records field that will store this value
This feature is only supported for portal tables based on linked record fields. It cannot be used with tables based on lookup fields.