I just wanted to update this thread. Another win for FlyerTalk!
I found a good D1 fare for MKE>ATL>NCE for next July ($2,600 RT) while browsing today. The dates work great for me so I decided to book it. Also, only 1 stop between MKE and NCE is often way more expensive than two stops via CDG or AMS. So this was perfect.
The issue is that I had an eCredit and a gift card and wanted to use both. The website, however, made it look like that wasn’t allowed. I was about to give up but I decided to search FlyerTalk and found this very helpful thread.
Thanks to the info here, I reached out via the messaging system and within 20 minutes the agent was able to book the flight using card + eCredit + gift card.