RE: How to enable comment field under direct delivery in purchase order and sales order
Hi Muhammad,
The Allow Edit is set to No in the properties of the form ds or in the code.

You may try the following steps:
1) set datasource to AllowEdit = true;
2) in datasource's init() method after super() simply call:
purchLine_ds.object(fieldNum(PurchLine, MCRDropShipComment)).allowEdit(true);