Hi there!
I'm here to share some workarounds on how you handle your shipping and your inventory.
Since QuickBooks Online does not handle landed cost. You can add a portion of the shipping to each item total. On the bill you can select the item and enter the quantity received and click over to total amount and enter item cost plus a portion of the shipping. When you click out of the total cost block QuickBooks will do the item rate.
Use this article the detailed information: Understand inventory assets and cost of goods sold tracking. It also shares how to compute the average cost and know which report will help with inventory management.
If there's a need to adjust the item's quantity, check out this article: Adjust inventory quantity on hand in QuickBooks Online. It guide you through the steps.
Don't hesitate to leave a comment below if you need more help with this. I'm always around to provide the information that you need. May your day be wonderful as you are.