Add Heading 3 in the right navigation menu

[GabrielaDoc]

I inserted in a page several Headings: Heading 1, Heading 2, and Heading 3.

Heading 3 doesn't appear in the right navigation menu.

Thank you.

[aaronthayer-zoom]

Chiming in on this open request: This is absolutely a feature improvement I'd love to see.

Explicitly, it would be great to both add Heading 4 to the editor and also recognize it as H4 within MD files, and add Headings 3 and 4 to the floating TOC. I assume the current, and very clean, floating TOC would need some reconfiguration to accommodate more headings, and probably why they aren't currently supported.

Four heading levels would be great for most tech doc use cases. We tech writers try and shy away from H5 and beyond anyway, instead favoring a rewrite or restructure of the content. Still, proper H1-4 levels for complex content cover the bases.

Thanks!