Thanks for being a member of the QuickBooks family. I'll be happy to assist. With QuickBooks online, you can import specific data to your account to save time and effort. That being said, importing an excel file that has an all employees time worked on projects into QuickBooks Online is not an integrated feature of the system.
Feel free to reach out if you have any other questions.
Check out Transaction Pro Importer. It works with both Desktop and Online versions. @JamesM can give you a special link from a Quickbooks site that gets you a better price than offered on the Transaction Pro website.
If you search these forums for 'transaction pro' you will find other posts made about its ability to import, export, etc.