If the "Table of Contents" app block or app embed does not appear in the theme editor, check the template you have open and your plan.
App blocks and app embeds are available only on the following templates.
Blog posts: every plan
Products: Regular plan
Pages: Regular plan
Collections: Regular plan
Limitation: You cannot add them to other templates, such as the home page, blog listing, or search results. Product, page, and collection blocks for the Regular plan do not appear in the picker unless you are on the Regular plan.
On an Online Store 2.0 theme, add an app block to the template. On a vintage theme, use App embeds in the theme editor.
For details, see App Block vs. App Embed.
Uninstalling the app deletes table of contents settings data. After you reinstall, the app embed is off again. On a vintage theme, turn the app embed on again, then select "Save."
Note: Contact us before you reinstall. Settings data cannot be restored.
If the above still does not solve the issue, contact us through the contact form.
When you contact us, include the following information.
The store's myshopify.com domain
The theme name
The template you have open
The items you have already checked