I appreciate you for sharing your feedback with migrating QBSE data to QBO.
We don't take this lightly and recognize its impact to our customers. While we don't have a direct tool to transfer data from QuickBooks Self-Employed to QuickBooks Online, you can consider checking for third-party apps that handles data conversion between QuickBooks platforms..
Visit our applications website here: https://apps.intuit.com/app/apps/home
Having the ability to move Mileage automatically after upgrading a QBSE account to QBO is convenient when added to the program. I'm making it my top priority to send this request to our developers.
If you need additional help, feel free to reach out to me. I'm always here to provide further assistance with anything QuickBooks related. Have a good one!