Include a full table of contents in your Sphinx HTML sidebar
sphinxcontrib-fulltoc is an extension for the Sphinx documentation system that changes the HTML output to include a more detailed table of contents in the sidebar. By default Sphinx only shows the local headers for the current page. With the extension installed, all of the page titles are included, and the local headers for the current page are also included in the appropriate place within the document.
See the project documentation for more details.