Inventory marking & UnMarking in D365FO X++

 //UnMark

InventTransOrigin::deleteMarking(InventTransOrigin::findByInventTransId(<CurPOInventTransId>).RecId,

                        InventTransOrigin::findByInventTransId(<RefSOInventTransId>).RecId,

                       <Qty>);

//Mark

InventTransOrigin::updateMarking(<CurPOInventTransId>, <RefSOInventTransId>, -1* <Qty>);