Welcome to the Community, @userkee.
Uploading invoices in QuickBooks Online (QBO) is pretty quick and easy. However, the option to change the format to 3 decimal place is currently unavailable. You can see other formats available by going to your Accounts and Settings.
Being able to widen the customization option for decimal is a good idea. While we continue to work on improving the features of the product, you may visit our Blog site. This will help you stay updated with the latest QuickBooks news and updates. Here's the link: QuickBooks blog.
To learn more about uploading invoices in QBO, check out this article: Import multiple invoices at once.
Reach out to me in the comment section below if you have any other questions or concerns. I'm always here to help. Have a good one!