Hello there, Stephen. I'm here to provide information about your online transaction in QuickBooks Online (QBO).

When you connect your bank to online banking, you'll need to contact your bank to determine where the transactions will be downloaded. In your situation, since the parent account is connected to QuickBooks, all the transactions will be downloaded to the parent account.

You cannot connect the sub-accounts/individual accounts since the parent account is already connected. You only have the option to connect either the parent or sub-accounts.

You can check this article for a more detailed guide: About bank or credit card subaccount setup.

You may check this out to learn how to Categorize online bank transactions in QuickBooks Online.

If you have more questions related to banking, feel free to reply. We're always available.