Diagrams could be either included inline into confluence page in this case you need a plugin
Or you can render them offline before uploading and attach renderings to the page as PNG or SVG. Rendering is done via Kroki server, default option uses public instance, but to avoid throttling or protect private data one could install a local copy of Kroki in their own environment
Adding support for Mermaid diagraming
Diagrams could be either included inline into confluence page in this case you need a plugin
Or you can render them offline before uploading and attach renderings to the page as PNG or SVG. Rendering is done via Kroki server, default option uses public instance, but to avoid throttling or protect private data one could install a local copy of Kroki in their own environment