Mermaid for google docs
When you add a graph, you can type mermaid code in the left panel and see the preview on the right update.
Feel free to change the theme. Then click "insert" to generate the image and add it to your document.
If you do a typo, the plugin will try to tell you where
You can always get the source code of your graph by checking its alt texts
Check out the mermaid website to see what graph types are avaliable