Compare viz-js.com 
Edotor.net improves viz-js.com with syntax awareness and refactoring support.
Screenshot of Editor
After brief experimentation with the editor, I looked for source code.
The enabling technology for this language awareness in the editor is Language Server Protocol (LSP)—which also enables vscode's innovation. site
Edotor's author implemented LSP support for DOT: github
Edotor currently uses viz.js under the hood.
Our graphviz plugin started out using viz.js but we switched to hpcc-systems/hpcc-js-wasm. Should we offer a PR to the edotor author?
See About Graphviz Plugin and github
See Graphviz Viewer
exploring-edotor