Hi there, BZaman. Allow me to share with you some information about importing suppliers' credit notes to QuickBooks Online (QBO).
At this time, we don't have a direct way of bringing the supplier's credit note into the system. As a workaround, you can either upload them as bills or use a third-party tool that you can integrate with QuickBooks. You can look for one through the app centre. Here's the link: https://quickbooks.intuit.com/app/apps/home.
Otherwise, you can check out the solution provided by Fiat Lux -ASIA for an additional option.
On the other hand, here's how you can import customer credit notes to your account: How to import credit notes.
In case you want to get your data out from your QBO account in the future, you can use this link as your guide: Export Data out of QuickBooks Online.
Let me know if you have any other follow-up questions about importing transactions to QBO. I'm always here to help. Keep safe!