Mermaid is great for simple stuff. If you want a more advanced approach where you can even have multiple levels. Lool at c4. The best way to do c4 without paying a dime I think is https://likec4.dev/
But again, for simple stuff, mermaid! It's also natively supported in a lot of markdown renderers, like gitlab
But again, for simple stuff, mermaid! It's also natively supported in a lot of markdown renderers, like gitlab