Writing code as text is fine. But I'd love to see the idea of a "call graph" become a first-class citizen as a programming tool. What's the point of building modular abstractions if you still need to glue them together with text?
If I have a bunch of libraries that more or less do what I want and all my program has to do is glue them together (this is common in scripting scenarios), then I could just draw it up in a GUI like Gephi and cross-compile it to a script, instead of writing the script by hand. Complete separation of data flow from the implementation of that flow.
I imagine you could do this pretty easily in a language like Haskell (since everything is a function call) or Lisp (where everything is "data") so you don't have to implement special logic to figure out how particular nodes should behave. You could also do this for "explicit" DAG engines like Make, Airflow, and Luigi.
[0]: http://www.graphviz.org/content/dot-language [1]: https://knsv.github.io/mermaid/
EDIT: this ([2]) turned up in my Googling. I suppose there's a good reason nobody uses it?
If you are interested in this you should check out a company called Mendix, which is building a SaaS platform for building applications using graphical tools, and the Eclipse Modelling Framework, which is a huge project aiming to add modelling and code generation capabilities to Eclipse (in my experience it is slightly academic, in the sense that you often encounter bugs or cryptic errors in practical use).