I'm here to provide you the help that you need with inventory tracking in QuickBooks Online, blane_sticksvines.
Adding everything that you buy and sell is one of the best ways to properly track your inventory. You'll want to make sure that an invoice and sales receipt is created to track what you sell.
Also, to properly account for purchases, you can create a purchase order and copy it to the bill. But before doing so, ensure that you already have set up the items in the Product and Services List and everything in inventory will just flow and run smoothly.
Here's an article that you can check out for more information: Add Inventory Products In QuickBooks Online (QBO).
On the other hand, you can match existing entries once the system recognizes the suggested matches in the Banking tab.
I've added these article for your future reference:
Feel free to let me know if you have any other concerns with the inventory. I'll always be right here to help you anytime you need it.