You need to create sections with relevant headings in Google Docs. Since Google Docs is a web-based app, the steps to add headings remain the same on Windows, Mac, and the top Chromebooks.

click Insert > Table of contents in the top menu. Creating a manual table of contents involves structuring it to match the document outline and linking items in the list to the headings. Google Docs ...

All you do is insert headings to make the outline and create tabs as you go. Our guide covers the importance of creating a Google Docs outline and what you can do with it.

You can create & add a document outline in Google Docs using this guide. Difference between Table of contents & Document Outline explained.