The option to delete multiple transactions in the bank register is unavailable. You will have to delete them one at a time.
I'll be sure to forward your request to our product engineers. They are the ones who update QuickBooks and might include this option in the future.
You can visit our blog by clicking on this link: https://quickbooks.intuit.com/blog/. This is where you can see the new features added in QuickBooks Online.
Please let us know if you have additional suggestions or other concerns. Thanks.