Create a sales order of type – OR in Tx- VA01.
Provide sold to party and the items. Now to block some item go to Reason of Rejection.
For each item we can set what is the rejection reason. Now we need a new rejection reason.
Go to Tx- SPRO and navigate along the shown path.
Click on new entries.
Create a new rejection reason and save & back.
Now try to create a new sales order and check the new rejection reason should appear.