Optional dropdown section

[bkmgit]

It would be helpful to have a collapsible dropdown section for optional items to be included at instructor discretion. The styling for {: .solution} can be used as a starting point for this, modifying the title to optional and the color.

[maxim-belkin]

It's definitely doable but what are use cases for such a collapsible section?

[josephmje]

I think this feature would be really useful as well! Jupyter Book has a nice implementation where the title of the dropdown can also be customized.

I think it would help with focusing attention. You could add a hidden "Find out more" section that may go beyond the scope of the lesson but curious learners are welcome to try it out on their own time. Or if you had some code or functions being used to download data or for visualizations (any bits that act as a helper for the lesson but aren't integral to the core objectives), they could also be added here.