You can change the value to something different by going to:
Portal Tables
Click on a linked record field
Fields section
Record title
Choose Select another field
Set Custom field for record title value (Optional)
💡 Note: Attachment fields and linked records field types cannot be selected for this feature.
Troubleshooting:
If you see the error message 'Could not find a primary field for the table,' check that all linked-record fields, where the 'Record title' is set to 'Select another field,' have a custom field selected.