So on the default Sales Order (or PO, or Invoice, etc) screen, hitting the screen "Save" button seems to include the actions involved for the green "Update" button for the Line Item grid. So if I enter an item without an indicated Qty, hitting Save or Update will set the Qty to one, and insert that line as a record into the Line Item Table.
Enter my custom PO screen. For some reason my Save button no longer performs the same actions as the green "Update" button. Saving the screen is no longer adequate: unless I hit the green "update" button after entering line Items, they'll disappear from the grid if I reload the PO.
Can I access the action set involved in that green "Update" button to copy over to my "Save" button? Looking at my Sales Order screen, where the Save button is customized but still manages to perform the "Update" actions, I can't see any relevant difference, so I'm confused as to why the button functionality changed.