To re-categorized transactions that were already reviewed and accepted to QuickBooks, you have to Undo those transactions from the Reviewed column.
Click on Banking at the left pane, then select Banking.
Pick your bank account from the result, then go to the Reviewed column.
Look for the transactions from the result, then put a check-mark on the box beside it.
Tap on Undo so you can categorize them, then the transactions will go back to the ForReview tab.
Please know that we aren't able to create a rule for the transactions that were already downloaded to QuickBooks. You can create a rule for the incoming transactions from your bank. For additional reference about setting up and using banking rules for downloaded transactions, read this article.
To rules add and recategorize netIransactions that I already reviewed and accepted
Allow me to chime in and provide additional information here in the Community, @earthenescapes.
Once you create bank rules, it'll only take effect on your future transactions in QuickBooks Online. For those data that you need to undo and recategorize from the bank feeds, It needs to be changed manually from the For Review tab.
To ensure you'll no longer need to make changes individually, I suggest using the banking rules. I'm adding the steps below on your behalf: