First, to the immediate point: Ropes are not talked about much outside of whitepapers and undergrad data structure courses. This is a shame, even if ropes are only useful on very long strings. More discussion, more documentation, and more attempts to use ropes are not a bad thing, even if nothing "practical or necessary" comes of it. (And I would say that a text editor is quite practical!)

Second, it's completely reasonable to imagine data-structure-driven improvements to the task of writing source code. Imagine, for example, an AST editor. There are tools like org-mode and paredit which are halfway to true AST editing, and plenty of languages have tooling sufficient to support it, if there were demand. An AST editor would, of course, generalize the lessons here about ropes to pretty-printed ASTs, but there's no innate reason why it couldn't be done.

Third, a meta-comment, to address your comment elsewhere in the thread: "There are, of course, computer science concepts that are very smart. But we don't need these to save us from slow software, because today's slow software problem is just the result of people doing bad things in layer upon layer. We have to stop doing all the bad stuff and dig us out of the hole we're in, just to get back to neutral. Once we are back at neutral, then we can try thinking about some computer science smarty stuff to take us forward."

There are assumptions here about the nature of CS. CS is a science of abstractions. Complaining about layers in CS is complaining about the very nature of CS. Software is slow and insecure and hard to use because the tasks that we demand of software are extremely complex and our human processes for creating code are not sufficiently high-level, powerful, and expressive enough for us to design good systems on the first try.

Whenever somebody says, "I have removed a useless abstraction," they usually forget to also say, "By replacing it with a useful abstraction."