Collapsible blocks let you contract or expand sections of your document (if they are located below a header), to provide a cleaner look. To get started, click on the arrow to the left of a header. This lets you toggle whether the content for each section is collapsed or expanded.
Shift + Click to collapse or expand for everyone on your team, by default.
You can embed a table of contents directly in your docs to streamline information via the /toc command, too.