Line Numbers are now an option for transactions with Line Items:
Quote, Order, Invoice
Request, Purchase Order, Bill
Item Adjustment, Warehouse Transfer
Line Numbers enable new features to:
Show - click to show the Item
Insert - click to add a row above or below
Sort - use the Sort button even on saved transactions
Reorder - click to Move To another row
This Solution describes this setting. (6628)
Line Prefs
Update Custom Forms