i dont think this will help in a sense @lubos.
the serial number feature should be optional feature. if user has single type of item with different serial number then it is first to be activated in inventory item. if this serial number item is selected then it by default showing up in purchase and sales invoice both.
so when purchase invoice is created the product with all the serial numbers used in the in the purchase invoice will be added to inventory items. when a sales invoice is created then first item name is selected and it will show the available serial number of products available in that item list. that way it will easy to track down of each serial number product purchased from whom and sold to whom.
As the main purpose of our manager software is to account for everything in it.
few discussions already happened Record individual serial numbers for inventories? - #3 by jamesaepp
dont know if it makes a valid point.