Requirement is that "Ability to Add items to order when delivery already created without deleting delivery"
Ideally, if delivery is already created and item is added to sales order, they would like to reprint the delivery and have line 2 automatically pull from sales order.
How to achieve this, thanks in adv,
Automatically adding items to an already created delivery is not a good idea - this is best kept a manual activity as all exceptional cases.
As for the manual option:
If you are allowed to add items to the sales order (no custom development stopping you for example) and they can be shipped with the same LF delivery (shipping points, dates, partners etc.) and if the delivery is only created, but not planned or issued (assuming again a standard system), I cannot understand why your end users ask you such basic questions - this should be covered in their initial training on delivery processing.
Anyway, if such cases occur very often, then somebody is not doing a good job communicating with clients or with colleagues - it could be order entry errors, or failing to explain clearly until which date/time a customer can make changes to an existing order, or creating deliveries too early, or changing product codes for some reason and not informing everybody - plenty of possible scenarios, which can be addressed at management level.