I just stumbled across this and it seems like a great idea: http://blog.duangle.com/2015/01/conspire-programming-environment-for.html
Select group of nodes -> compact -> replaced with function with correct input and output nodes.
I’d use this a LOT if it existed. It’d be a lot smoother than creating functions in advance or by detaching into a different UI as you need to create a function. Sometimes it’s just nice to maintain your current editor context.