Hi there, @abcdaccountant.

Thank you for posting in the Community. Allow me to help share some additional input about activating the enter key for saving a transaction.

Currently, the keyboard shortcut for saving transaction is to press Alt + S or Alt + Shift + S for Firefox and Chrome. As mentioned by my colleague MorganB, the option to set the enter key as the navigation or saving button isn't available. 

I've also attached an article for additional reference about keyboard shortcuts: What are the keyboard shortcuts for QuickBooks Online?

We value your willingness to help us improve our products. I'll make sure to let our developers know about your preferences by sending them a product suggestion. This way, they'll know what features should be added to make the program work better for you. 

That should get you back on track. I'm just a post away if you should have any additional questions about QuickBooks Online. I'll be happy to help you out. Have a great rest of your week.