Allow me to provide some info about customizing the balance sheet in your QuickBooks Online Accountant account.
You can customize the balance sheet in your account using the steps provided by my colleague @JamesDuanT above. These reports are the same in QuickBooks Online and the QuickBooks Online Accountant Edition.
If you don't see these customization options, I recommend opening the program in a private browser where your web information data isn't saved. Then, you can customize the balance sheet to show non-zero balances. After doing so, you'll want to clear your cache and cookies to help prevent any loading or formatting issues within QuickBooks again.
I'm only a post away if you have any other questions. Best wishes!
One possible cause you're unable to customize the balance sheet report to show non-zero is a browser-related issue. I'd suggest logging into your QBO account via a private browser. This doesn't use the existing cache files, which makes it a good place to determine if there's an issue with the browser.
Here are the keyboard shortcuts:
Safari: Press Command + Shift + N
Google Chrome: Press CTRL + Shift + N
Mozilla Firefox or Microsoft Edge: Press CTRL + Shift + P
Once signed in, pull up and customize the report again. If you're able to see the options provided by my colleague, let's clear the cache of your main browser. This helps remove its stored cache so it'll function efficiently.
However, if private browsing doesn't work, I recommend using different browsers. They'll provide you the best and most secure experience with QuickBooks. For more details, see this article: System Requirements for QBO.
You may also want to consider memorizing the report in QuickBooks Online. Doing so will help you save the current customized settings for easy access in the future.
I'll lend a helping hand if you need anything else. Have a great day!