...
Mermaid Charts & Diagrams for Jira provides a an app that allows you to add allows you to add beautiful diagrams define defined with a textual descriptions. A documentation of the textual description can be found here https://mermaid-js.github.io/mermaid. To add a diagram to an issue, select the app as shown in the screenshot below.
...
In the app, This should add a new section to the issue looking as follows:
...
To define the diagram code, click the “Edit diagram” button and enter the textual description (Mermaid code) of the diagram in the editor and click “save”.“Save”:
...
After saving the Mermaid code, the rendered version of the diagram is shown. On this view, you can click the download icon to download the diagram as PNG image.
...