It's good to see you today, carstensph,
I can share some information about the inventory feature in QBO.
I just need more information about your concern. May I know how do you currently track your inventory? Any information you can share is extremely helpful to get past the problem.
Furthermore, you're able to markup your inventory in QuickBooks Online. You'll only need to make sure you have enabled this feature in your Accounts and Settings. Let me guide you how to do that:
Once done, you can edit your inventory and add the product price and cost. This way QuickBooks will automatically identify the markup cost of your item. Here's how to edit your products and services:
That information should get you on the right track.
If you're referring to something else, please feel free to loop me in so I can get back to you directly. Have a good one!