There is no need for bank connect to add banking transactions in QBO. You can manually add transactions. It's very simple.
Just create a new bank account:
Left Dashboard > Accounting > Chart of Accounts > Select NEW button at the top right corner and to add a bank account.
Once you've created a new bank account, go back to the Chart of Accounts page and select bank account in question and click "View register" under Action column. This is where you will see your Bank register with all bank related transactions. You can even manually add transactions here. Just select "Add ..." link right below Date column.
See screenshots below for reference.
Thanks for choosing QuickBooks Online (QBO). I can help you add a bank account with QBO.
Once done, go back to your Chart of Accounts to view these transactions.
Feel free to read this article for more information: Add and connect to a bank or credit card account.
You might want to visit our page for future reference: Getting started for QBO.
If you have additional questions, please drop a comment below.