Hi @Anonymous,
Currently, the ability to add e-signatures to emailed transactions is available only in the QuickBooks Online mobile app.
In the meantime, I recommend using the mobile app to use this feature.
Here's a link on how to download the app: https://quickbooks.intuit.com/community/Apps/How-to-download-the-QuickBooks-Online-mobile-app/m-p/186438.
Also, I encourage sending us your feedback. This way, our engineering team can consider your suggestion for product updates in the future.
Please leave a comment below if you have any questions.