We appreciate you reaching out to the Community, Kim. For now, uploading digitally printed signatures onto checks is unavailable within QuickBooks Online (QBO). I encourage you to add your vote for this one by sending a feature request in the Feedback section within QuickBooks. In the meantime, you have the option to manually add your signature or integrate a third-party app with QBO.
Furthermore, I'd like to provide you with this article as a reference for future use: Customize reports in QuickBooks Online.
Feel free to ask if you have any further inquiries about printing checks. I'm here to help you whenever you need it. Have a great day!