Moving around in lengthy documents is very easy using the Google Docs “Outline” tool. Simply stated, the outline tool bookmarks the title and all headings. This list of bookmarks is presented as a left sidebar to your document.
Click the the item of interest from the list and your document will move to that location. To turn on the outline feature click Tools -> Document outline from the menu. To close the entire outline, click the “X” to the right of the Outline sidebar title. You may also close individual items from the outline by clicking the “X” to the right of the item on the sidebar.
Source: Google G Suite