1. Change your computer sleep settings to remain awake always - this will use more battery life on a laptop so you would want to plug it in.

This does not prevent data loss during a power outage or a loss of internet service.

You can try downloading the desktop app of QBO while not guaranteeing you can work "offline" it might possibly save before sync - which would be what you need.

2. Create your invoices in Excel, which if you use the Office 365 version.can autosave while you work. Then import the excel sheet into QBO. You will need a third party app or be subscribed to QBO Advanced for ability to import more than just lists.