Let me share some information on you can manage your downloaded bank transactions in QuickBooks.
When you first connect your bank, you'd be asked to assign its appropriate type.
If you have several accounts associated with the same bank login credentials, you'd have the option whether to show it in QuickBooks or not. Once completed, the system will start downloaded 90-days worth of your bank transactions. You'd see it in the For Review tab on the Banking page.
From here, you can review each transaction and categorize it according to the specific income or expense category. You can read through this article for more detailed instructions about the process: Categorize and match online bank transactions in QuickBooks Online.
Also, I'm adding these articles as an additional reference to help you manage your downloaded bank transactions: