Thanks for reaching out to the Community forum, @muhannad-acc1.
You'll get an error message Transactions can have only one foreign currency at a time when you're using two multicurrency accounts in QuickBooks Online when setting up an inventory item.
To get this resolve, make sure you're using the same currency account for Inventory asset account and Expense account. You can check the video on this article for the detailed process: How to Set Up Products & Services: Non-inventory, Service Items, & More.
For future reference, I'm adding some articles that you may find helpful:
If there’s anything else you need help with in setting up an inventory item, you can reach back out. I'm here to answer it for you. Have a great day!
