We've recently started planning UX for this feature. Hopefully we'll be able to start development soon. 

This is an interesting idea. Lets vote :)

You can create this kind of table of content using anchor elements. We're doing exactly that in our tutorial posts on help.webwave.me, for instance in this article. Please contact our support if you're not sure, how to create it.

You can create an accordion module useng interactions. Please contact our support for assistance if you're not sure, how to create it.

We've been searching for suitable plugins able to provide this functionality, that we could integrate into WebWave. Unfortunatelly no luck yet :(