Once done, you can go to the Products and Services panel and edit the items (if you already created one). Then, under the Income account or Expense account field, choose the sub-account you've created. Then, click Save and close.
Then, go to Projects to add transaction a transaction and choose the item with the sub-account in the Product/Service column.
Once you go to the General Ledger report, click the Gear icon and add the Account column to show the sub-account linked from the sales form transactions.
If you find the steps provided tediously, you can use classes to track income, expenses, or profitability by business
segment (available only in QuickBooks Online Plus and Advanced). You can check out this article for more details about class tracking: