After assigning a custom item field as either a Field Set or a Sort Field in Suite Commerce Advanced website we cannot edit particular custom field
this is because to prevent the user from deleting a custom field which is already used in “Field Set or a Sort Field”.
As a workaround, users will have to remove the custom field from being assigned as Field Set or Sort Field in Suite Commerce Advanced website follow below steps.
1. Navigate to Setup > Suite Commerce Advanced > Setup Website
2. Click the Search Index tab > Sort Field > remove the custom field from the list or
3. Click the Field Sets tab > remove the custom field from the list