I accidentally marked some payments into the savings, but they went into the checking... how do I update that?

I'm here to assist you in updating the account where your invoice payment will be posted, @jodiej1. 

To post your payment to your savings account, you can update the Deposit to account in your Receive Payment transaction.

Here are the steps to follow:

1. Go to the Sales menu and select All sales tab.
2. Find the payment transaction and click on Edit.
3. Update the Deposit to account to your savings account. 
4. Click on Save and close once you're done. 

Check out the following article for more information about getting a financial snapshot of your business as of a specific date: Run a Balance Sheet report in QuickBooks Online. It also covers how to compare the Balance Sheet report to different periods and why it may not show a correct balance or match with the register.

Moreover, you can customize your reports in QuickBooks Online by applying multiple filters to get all the information you need. 

Let me know if you need more help with your reports or anything else. I'm here to help you anytime. Have a great day!