We recently added new visualizations to mbeddr. These new visualizations are based on PlantUML, a textual language for describing UML diagrams, plus a renderer that generates the diagram itself (partially based on Graphviz). We’ve built our own SVG-based viewer, integrated into MPS, so we can use click-to-go-to-editor from within the picture. It is easy to build custom visualizations simply by implementing an interface and overriding a method that generates the PlantUML input text. The rest is automated.
PlantUML is highly recommended: works well, easy to use, and when we encountered a problem, we got a reply to our question quickly, and within a few days, there was a new version that fixed the problem. In other words: PlantUML is actively maintained and the community is alive!