You could play with this making a live coding function, but simply allowing text input and then taking that text and using it as another node’s input. You use this all the time when you make interfaces…you just have to take that concept further. It should be possible to build a type of modular interface that takes blueprint nodes and uses them to create widget’s that essentially function as the same thing, then make the changes propagate from the widget to the real blueprint node.
Making a shared editor though, that’s a doozy… Since Unreal still executes every blueprint sequentially, just like a line of code, you can run into trouble when you have to worry about replication. You’d be better off brainstorming on exactly WHAT concepts you want to have at play or play with, and go from there. The original Garry’s Mod is a perfect example. If you haven’t heard of it, I would check it out.