Starting in Tiki12, a new feature to allow adding an automatic Table Of Contents ("Auto TOC") has been added to the Wiki. And starting in Tiki23, you can have more options via PluginAutoTOC
Auto-toc can be enabled as admin through the admin panel in "Admin home > Wiki > General Preferences (Tab) > Section Automatic table of contents (Page Display before Tiki 15) > Wiki auto-toc"
You can also choose:
Auto TOC is not included in the print view of the page.
Auto-toc will add the TOC in two places.
Additionally, you can also see it in action in the screencast below.
You can disable it in some wiki pages. In order to do so, edit the page, go to the properties tab, and set "Page display options > Automatic Table of Contents generation" to "off":