I am searching for IDEs/editors that will allow me to collect and edit subsets of the same files in multiple different views. This is precisely Leo's cloned node feature: Changes in a node are mirrored in the clone and vice versa. An analogy might be symbolic links or aliasing in a file system. (This is not the same as copying a file where edits to an original and the copy are independent.)
Leo is very cool, but I'm wondering if this feature is available in other IDEs. I am happy to pay for ease-of-use, stability, and polish.
(Bonus: Can I do this in Jetbrains' MPS? It doesn't seem like it from my playing around.)