Good day, elaine14,

QuickBooks Online lets you create sub-accounts to help organize your income and expenses in a more detailed way.

The following steps will guide you through setting them up under your property, plant, and equipment:

1. Click the Settings ⚙ icon, then select Chart of Accounts.
   
2. Hit New.
   
3. Select the account and detail type.
4. Enter a unique name for this account. 
5. Mark Is sub-account, then enter the parent account.
6. For the as of date, tell QuickBooks when you want your account to start, then add the Balance in the account as of the date you choose.
7. Select a Default GST Code.
8. Click Save and Close.

You can also refer to this article for more details with the steps above: Create subaccounts in your chart of accounts in QuickBooks Online.

Let me know if there's anything else you need, and I'm always glad to help you out.