Create TOC with multiple level

There are many ways to implement your required, but here's what you can try. 

1. Create a section-container component (sling:superResourceType parsys or responsive-grid).
2. The section-container will allow dialogue configurations to include a title & title header level.
3. The section-container allows content components be added in its content body.
4. Create a TOC component;
5. The TOC component with one to one relationship with a Sling Model.
6. The TOC component will have logic to search for all section-container components configured on the page and display the title & title header level properties.
7. Complete.

The page will only be constructed with the section-container component. While the TOC component sites on top of the section-container component.

JCR View:

/content/my-site/page/jcr:content/par/toccomponent
/content/my-site/page/jcr:content/par/sectioncontainercomponent0
/content/my-site/page/jcr:content/par/sectioncontainercomponent1
/content/my-site/page/jcr:content/par/sectioncontainercomponent2
/content/my-site/page/jcr:content/par/sectioncontainercomponent3