Editors can insert a table of contents into a page with a simple click — headings and subheadings will automatically update as content is added to the page. A table of contents also helps guide editors to organize their content in a structure that is easier for readers to understand. Site viewers can quickly navigate through sections of a page by clicking the desired heading and automatically jumping to that section within the same window. From https://gsuiteupdates.googleblog.com/2019/02/table-of-contents-sites.html