It's important that all your transactions are entered correctly for your books to be well balanced. QuickBooks Online is a great tool able to help you keep track of sales and expenses so that you can see the profit of your business. I can provide some information about GIFI mapping.
The GIFI mapping tool isn't available within QuickBooks Online itself, but the QuickBooks Online Accountant version has the ability to map GIFI codes. You can view this information as well as how to map GIFi codes to your chart of accounts in this article.
If you have any other questions, feel free to reach out here.