Flexible Table Of Contents
This module generates a table of contents block for individual fields within your content. You can place these field-specific TOCs in your layout to improve navigation, with options to customize the elements included in the table of contents.
Description
This module creates a Table Of Contents block for each field that you enable. You can then place each block wherever you need in your layout to enhance the navigation experience. The table of contents generated with this module will be contained to the specified field rather than to the whole page or to the whole node.
Usage
Installation
Install it as any other Drupal module.
Using the module
To create a TOC block just go to content type (or entity) you want and click on Manage Display. Find the field you need and click the configuration gear icon on the right. This will present the configuration form for that field.
From there you can activate the generation of the TOC block for that field in that particular entity bundle (your content type). You can also add a CSS selector that will be used to generate the TOC items. You can input here things like h2 or strong, .header, …
Once you have your field configured the TOC block for that instance will be made available to you.
Also consider
The Table of contents module and the jQuery Table Of Contents have different approaches on how to generate a table of contents automatically. Explore those options to find which one serves your needs better. See also this comparison of TOC modules.