We have some supported third party apps that can automatically sync data between FreshBooks and QuickBooks Online (QBO), such as FreshBooks by OneSaas. You can check these apps by clicking Apps in the left navigation bar of QBO.
If the available apps are not suitable for you, it's best to reach out FreshBooks. They'll be able to provide you the proper steps if there are other ways of transferring your details from the app to QBO.
Feel free to
keep me posted if you have other questions about connecting third party apps
with QuickBooks.
As an alternative to OneSaas, you can also sync your QBO and Freshbooks data with the help of Skyvia (https://skyvia.com/data-integration/integrate-quickbooks-freshbooks). It`s the cloud-based no-coding solution, with flexible scheduling settings and user-friendly UI.
I reached out to Skyvia, and was told that they could transfer over all data except invoices--which is one of only two things I needed, so not much use to most people.