service/documentation.md

@@ -664,3 +664,10 @@ See also [this LWN article](https://lwn.net/Articles/822969/).
 
 [vale]: https://errata-ai.gitbook.io/vale/
 [nodejs markdownlint]: https://github.com/DavidAnson/markdownlint
+### Charts
+
+We currently use [Graphviz](https://graphviz.org/) to draw charts, but have also used
+[Diagrams.net](https://www.diagrams.net/) (formerly `draw.io`). Other alternatives:
+
+ * [Mermaid](https://mermaid-js.github.io/mermaid/#/) - builtin to GitLab and GitHub
+ * [Knotend](https://www.scottantipa.com/why-knotend)