If I want to undo adjustments on the History by account page (under Accounting -> Reconcile), is this possible? It only shows me View Report / Print.

Thanks for joining the Community space, @office197.

Yes, you can undo adjustment in the History by account if you're using QuickBooks Online Accountant. In your case, you can manually unreconcile the transaction from the bank register and change each status from Reconcile (R) to Blank, or Cleared (C). 

Here's how:

1. Select Accounting in the left navigation menu.

2. Go to Chart of Accounts tab.

3. Double click your bank register to view its transactions.

4. Find each transaction you see on the reconciliation report and click on it.

5. Hit on the Reconcile field until the R changes to blank or C.

6. Tap the Save button, then click Yes to confirm. 

You can also invite your accountant as a user of the program. They have a special tool to undo entire reconciliation. You can have them perform the steps through this article: Undo Client's Reconciliations. After that, your accountant can unreconcile your account again.

I'd suggest visiting this article: Reconcile Workflow. It provides information about starting, fixing any differences, and completing the reconciliation process. Click the link beside QuickBooks Online in each scenario. 

Lastly, I've got you this helpful article you can read for ideas about reconciliation report: How do I view, print, or export a reconciliation report?

Please leave a comment below if you need further assistance. Know that I'm always ready to help you. Have a nice day.