Hello! I have another question. Is there a way in Special Orders to tell which line of Sales Order is linked to a line of a Purchase Order? I tried to find a field but with no results.

You can achieve this with a saved search by either referencing the created from record, or applying transaction fields.

Thanks Nick. But in that case I am getting the link between a line and a record. I was looking for the link between line and line that exists (it is used for example for commits) but maybe cannot be retrieved.

Not sure I follow. The following saved search produces the Line ID on both the Sales Order and the Line ID of the related line on the PO: