Hello there, @fdyste.

As mentioned above, You can use a supported third-party application that can automatically sync data between FreshBooks and QuickBooks Online. I also advise contacting FreshBooks support. They can provide you the proper steps or other ways of transferring your data from the app to QuickBooks Online.

You can also use this link to search for an article if you need some steps or information while using QuickBooks Online: Help articles.

Let me know if you have any other questions. I am always here to help.