TOC is a good way to explain it.
I was hoping to find more ways use nested cards. So in this case it would be that instead of a label on the iceberg (or any other smart diagram, layout, or within a column, I can put a nested card so I can expand on the idea.
This would help create more interactive gammas rather than simply linear presentations / flows.
An example might be the way a "hotspot" functions in a LMS authoring platform, or popups in a web app.