How do I rename an existing chart name, i.e., "Bank" to Key Bank - Checking?

Yes, you can, brewster. 

We'll have to edit the Account name or Name in the Chart of accounts section to rename your existing account. I'll gladly show you how to do this below.

1. Go to Settings or the Gear ⚙ icon and select Chart of accounts.
2. Find the account you want to rename.
3. Click the drop-down arrow beside the View register option under the Action column.
4. Select Edit.
5. If you're in Accountant view, edit the account's name in the Account name field. 
6. If you're in Business view, rename the account in the Name field. 
7. Click Save or Save and Close.

Additionally, I encourage you to reconcile your accounts in QBO regularly (every month). This helps monitor your income and expenses and detect any possible errors accordingly. You may want to check out this article as your guide in doing and fixing reconciliations in QBO: Learn the reconcile workflow in QuickBooks.

Please keep me posted if you need further assistance managing accounts in the chart of accounts in QBO. You can add your comment below, and I'll gladly help. Take care, brewster.