As of the moment, we can only enter the cost of the item and the sales price when setting up an inventory item.
In the meantime, what you have practiced is the best option to set this up.
I suggest sending the same message to our developer team by feedback. This way, they'll know of the things need to be added and improve the product preference which will help you and other users about the inventory set up. Simply go to the Gear icon then select Feedback.
Let me know if you have any other questions by clicking the Reply button. I'll be always around to help.