Thanks for reaching out to the Community. I hope your day is going great.
As of right now, there isn't a way that you can create a file within QuickBooks Online. The only option would be to export the data out to a CSV file and make adjustments to the CSV. You could then send your CSV file to the bank. Below I've included the steps for exporting your bank register.
1. Open the Accounting menu.
2. Choose Chart of Accounts.
3. Pick the correct account and click View register.
4. Select the export icon at the top, next to the print icon.
5. Your file will automatically download.
That's all there is to it. Please let me know if there is anything that I could assist you with further. You can always reach out to the Community or me anytime you find you need help. Take care!