[tobych]

JetBrains IDEs can do almost this using the PlantUML plugin (see my comment above): you just have to write a little graphml code to show the PNG. It's not inline with the source code, but in a separate pane. But a documentation generator (such as Sphinx) could show the image inline, with a little plugin.

[criddell]

I have done this with a documentation generator (doxygen) but I want it in Visual Studio. There is a plugin for it, but it's pretty buggy. It would be nice if it were a core capability.