We really do appreciate this feedback, @Lumberprincess.
 
We wanted you to know that providing the best possible solutions to our customers is our main goal here in the Community.

For now, the option to add a new Detail Type accounts is unavailable in QuickBooks Online. However, you can create a sub-account and match it to the closest parent account. 
 
Let me send feedback to our developers so they can check it and probably add this feature in any future updates. 

I encourage you to visiting our QuickBooks Online Blog to stay current with our news and updates.

Please know that you're always welcome to comment anytime if you have other concerns.