Add subsections

[paulo-ferraz-oliveira]

(I'm going to write my text inside code blocks so it gets easily distinguished from the actual text blocks I wanna talk about)

At the moment, Livebook does sections, like...

This is a section

This is text inside the section

This is another section

This is text inside another section

Have you considered subsections? (and maybe the ability to
turn a section into a section's subsection)

e.g.

This is a section

This is text inside the section

This is a subsection

This is text inside the subsection

Of course, in this example, there doesn't seem to be a huge
difference, but if I had a ToC, like Livebook does, it could.
I see that I can add subsections as level 3 Markdown, but it
doesn't get "rendered" in the ToC. Maybe that's also a
possibility?

Cheers. And keep up the good work, Livebook is a wonder.

[josevalim]

Currently you can add subsections within Markdown! Just use ### (or more) and they won't appear in the TOC.

[jonatanklosko]

We manage the top-level sections for several reasons: (a) they encourage grouping cells in a meaningful way (b) they allow for batch operations like moving/deleting cells (c) we have the idea of branching sections that fork evaluation and run in parallel. I think that's a reasonable amount of granularity. Note that currently all cells need to be in a section, but with lower-level sections it wouldn't be the case and so managing those could be confusing. Alternatively, we could handle subsections introduced with ### in some special way, but I'm not convinced we should.

Also, if a notebook grows so large that it requires a more involved TOC, I would consider splitting it into several notebooks and an index.livemd file with relative links to those :)

[paulo-ferraz-oliveira]

Thanks for this, @jonatanklosko. You're right, maybe the Livebook just grew too much and we should split it in several smaller ones. We are using this for a presentation, so it felt kind of natural to keep it all in the same document, but we will experiment with alternatives.

[jonatanklosko]

You can also make each notebook link to the prev/next notebook at the end if you want to improve the flow of this approach.