I feel like every few years GUI based workflow tools make a revival, but then slowly die out. In the 1990s the selling point was that your "business logic" could be written by "the business" instead of those expensive programmers, and we all know how that panned out.
There is obviously something here, however, especially when you consider what people are doing with Simulink. But why do these tools remain niche? Is there some threshold of complexity past which these tools don't scale well, but source code does? Considering these tools are effectively representations of a program's call graph, could there be a future where I toggle between text and graphical versions of my program depending on what works best?