Just a reminder that JSONata on Node-RED already has moment.js built in.
That's great. But still the issue is adding more code to debug. Every node I want to debug would need this additional code, and all of them unique since they typically have different format. And need to be cleaned up afterwards. Instead of debugging directly which works everywhere all the time with no clean up. If I went down that route, I'd rather just do it in a function node with normal js (and moment) instead of dealing with jsonata.
As people have said, if someone provides a working PR , it will be considered for the next Node-red release.
In the meantime, another possible work-around is an inject node, db query or a function node somewhere along your flow to add a new message property msg.mydateformat.
Set the debug node to display this rather than msg.payload
