Currently, QuickBooks Online doesn't allow customization of cheque templates, Corkerys.

The cheque templates are pre-designed to work seamlessly with standard pre-printed cheque formats, ensuring compatibility and ease of use for most businesses.

While you can't directly customize the layout, such as adding lines to move information. QBO provides tools to adjust printing alignment. This ensures your cheque information aligns properly with your pre-printed cheque stock. For more details, refer to the article: Configure and troubleshoot your print settings for printing cheques in QuickBooks Online.

Feel free to return to this thread if you have follow-up questions.