I would absolutely love the possibility to collapse text. Dropbox Paper's implementation is quite good. Anything under a heading (#, ##, or ###) can be automatically collappsed and a link to that section is available. Also, this automatically creates a navigation pane, like Google docs does.
The value of this approach, to me and our company workflow, is that it allows us to create content, discuss it 'live' on the document with clients, and only show the part we are currently focused on. On longer notes, it also is much easier to navigate.