GraphViz is great, like Markdown. I recommend https://edotor.net https://edotor.net for online use: 1. No set-up, no accounts/registration. 2. Free, no ad

GraphViz is great, like Markdown. I recommend https://edotor.net https://edotor.net for online use: 1. No set-up, no accounts/registration. 2. Free, no ads. 3. Simple, pleasant UI with variable/keyword autocompletion and even multi-cursor find/replace! 4. Your graph is saved in the URL so sharing the link lets others play with a copy of your graph. I usually link-shorten the URLs since they're long: https://bit.ly/edotor-example-1 https://bit.ly/edotor-example-1 https://bit.ly/edotor-example-2 https://bit.ly/edotor-example-2