Modify the Product Classification Attribute Reference Object Picklist

For each object you want to make available for extended attributes, add the API name to the Product Classification Attribute object.

1. In Object Manager, find and open the Product Classification Attribute object.
2. In Fields & Relationships, find the Reference Object field.
3. Under Reference Object Picklist Values, add a picklist value for the object. The value must be the API name of the object.