We're glad you're here, HiddenGem.
I appreciate you joining us in this thread. I'm here to address your concern with adding a convenience fee in QuickBooks Online (QBO).
Giving you the best experience in processing customer's payments is what we aim for. However, adding a convenience or credit card fee automatically on the transaction in QBO hasn't been made available. I recommend following the workaround steps above provided by my colleague, Jen_D.
Just in case, you might want to check this article that will help you get a better idea about credit card fees.
Please know that we are constantly improving our product's feature to meet your needs. Everything we have developed within the program derives from listening to our customers.
You can always check back for any product updates and feature enhancements through this link: https://quickbooks.intuit.com/blog/.
I'll also update you in this thread if I hear any changes about the option that you're looking for.
That should do it. I'm always around if you have any other concerns. Have a great day.