I appreciate your proactivity in finding the necessary steps to edit your opening balance. Mistakes happen sometimes, and I know how important it is to resolve them. I'll be happy to assist you with this.
Considering your screenshot and the information on it, the steps that you outlined in your post will only enable you to edit the Account type, Detail type, Name, and Number. You can indeed enter the opening balance when setting up an account in the chart of accounts, but to edit that value, you'd have to go a different route. Here's how.
Here are some articles for your reference.
It's also important to note that editing a transaction included in existing reconciliations in the program can cause problems in your bookkeeping. If you've reconciled in QuickBooks Online before, I'd recommend reaching out to an accountant to assist you with this task to ensure everything is lining up correctly in your books. You can easily invite an accountant to your books or find one in your area. Just head to the My Accountant tab to get started, then select Find a pro to help.
I hope this helps! Have a nice day.