Good day, cisca.
When you set up an item, QuickBooks Online will only use the home currency in the inventory asset account. You'll want to use the stock account for your home currency. Then, manually convert the amount from USD to your currency when adding the Sales price/rate and Cost.
I'm also adding this article on how to set up and track your stock.
If you need more help with QuickBooks Online inventory, please let us know and we will get back to you. Thanks.