If you want Tables of Content, try this one

The plugin does one thing and does that one thing really good. It just works.

I have Ultimate Addons for Gutenberg (UAG) installed and tried their block for Table of Content. It’s okay and it even has a preview in the editor, but ultimately I switched to Lucky WP Table of Contents.

After installation I was a bit disappointed that there was no preview in the editor, but now I think that is actually an advantage. And the configuration options are just top of the notch: general options on the settings page, individual options per post.

And the author is also friendly and supportive of his app. Five stars from me.