Hi there, bdeshazer.

Your QBO might be on a Business view. This can be the reason why you're seeing a different sets of buttons.

Let's switch it to Accountant View to see similar choices. Just go to the Gear icon and select Switch to Accountant View. 

Please take note that this only changes the appearance and will not affect your data. Feature, menu, and button names are different in each view, but the actions are identical in most cases. 

Here's an article about this for more details: Switch between Business and Accountant view in QuickBooks Online.

Once done, go back to your Chart of Accounts and check if you can already see the box for sub-account. 

I'd also like to share a couple more of our Community articles for additional references and guidance:

• Use Account Numbers In Your Chart Of Accounts 
• Manage Default And Special Accounts In Your Chart Of Accounts 

Don't hesitate to reply to me or post more questions in the Community if you need anything else with QuickBooks. We're always here to help.