I linked my bank account for transactions after 1-1- 2022. However, I now need to unlink and relink with all transactions as far back as possible. How do I do that?

You can use MT Online or one of the converter tools with a one time license (e.g csv2qbo @ $60) as a workaround.

https://www.moneythumb.com/?ref=110

I appreciate you for posting in the Community, Ron. You'll be glad to know that your transactions will not duplicate if you wish to disconnect and reconnect your bank account in QuickBooks Online (QBO). Allow me to share further details about it. 

As long as you categorize your bank transactions, QBO will not erase your existing accounting data if you disconnect an account from online banking. It simply prevents the program from downloading new transactions. 

Refer to these steps on how to disconnect:

1. Go to Transactions and select Bank Transactions.
2. Click the tile for the bank account.
3. Select the pencil icon, then Edit account info.
4. Tick the box for Disconnect this account on save. Please note that this option is unavailable if QBO is downloading new transactions. Wait a few minutes for the update to finish before trying again.
5. Click Save and Close.

Please see this article for more in-depth information: Disconnect accounts connected to online banking in QuickBooks Online.

When you reconnect, you may choose the period when QBO starts pulling transactions. Some banks allow you to download 90 days worth of transactions. Others can go back as far as 24 months. To ensure there are no duplicates, note the latest existing entry in the account before reconnecting.

Furthermore, you may want to reconcile your accounts in QBO to ensure they correspond to your bank statements. This way, you can guarantee that your books are balanced and accurate.

Stay in touch whenever you have additional questions about disconnecting and reconnecting your bank account in QBO. I'll be more than glad to explain further. Keep safe, and have a nice day ahead!