The moment you put on a transaction, it appears in the transaction form. Depending upon the status and the setup of the business will depend upon the ledger integrations, so if the status of a purchase line is received the stock is in, if you are recording GRNI there are ledger entries, if it is on order, there are no ledger entries, if it is purchased then the invoice has been processed and the appropriate ledger entries are created.
I suggest you put a single transaction on a new item and follow it through the stages depending upon your setup.
Arguably NAV is considerably weaker here, you do not see the item ledger entry until it is in stock, whereas the AX transaction screen shows you a potential transaction and its status, so you get a complete picture. How do you know from the item ledger entry screen there is an open sales order, simply put you cannot, because it only appears when it is shipped and creates a ledger transaction or not, but in AX you will see it as a sales order line on order.