Those buttons have been removed from the actual invoice in this version.
You now have a discount column and the add items well you now have to go all the way back the then main opening screen. The worst thing about that procedure is if you have items to add to your invoice that arn't in the list you have to make sure they are all in first otherwise you have to cancel the invoice or save as dravt then add the itme then go back in again and add it.
In the earlier versions this was able to be added straight from the item selection in the actual invoice. Myself and I believe a few others have requested this be put back to how it was.
Graham