I believe this is an available feature in Windows, and seems an easy accommodation to the growing number of Mac users. Many errors are caused by not being able to implement this feature. Is it coming? Account Edge has this feature, and is more Mac friendly...
Even in the old days when we used Peachtree, this was a standard. Why not, Intuit?
As of now, the default account for vendors is unavailable in QuickBooks Desktop for Mac.
We're constantly striving to improve our software. I suggest sending feedback directly to our product engineers. This is the best way to help us know what our customers' want. You can do that by going to Help, clicking Send Feedback Online, then choosing Product Suggestion. The more requests a feature has, the more it is to be moved to the top priority list.
We love to hear from you soon. Reach out to us if you have other concerns. Happy New Year!