Hello @MaddM,
I want to let you know that your voice matters and I'm taking notes of your feedback and submitting it directly to our engineers.
As of the moment, you can only undo your reconciliation by manually editing the Reconciliation status of every transaction that has been reconciled already.
I've got you this article to learn more about how you can manually undo your reconciliation: Undo and remove transactions from reconciliations in QuickBooks Online.
If there's anything else that I can help you with, please let me know in the comment section down below. I'm always around happy to help.
