Hello @johannaox,

Thank you for posting here in the Community. I'm here to help you set up SKUs in QuickBooks Desktop.

Currently, a specific field for SKU is unavailable. As a workaround, create a custom field for the additional details in the item information.

Here's how:

1. Click the List tab at the top menu bar.
2. Select Item List.
3. Press New.
4. Click Custom Fields.
5. Add a new one. 
6. Hit OK.

I've attached the following article that can help you with updating item information in QuickBooks: Add, edit, and delete items.

Please let me know if you need anything else regarding managing inventory in the Desktop version. The Community and I will be here to help you.