MaximeB

This plugin will check if there are some hidden meta tags with noindex and warns the author of the article. The warning is only visible for the author of the post, or the admin(s).
Features :
<ul>
<li>Check the content of a post and detect the presence of meta tags with robots/noindex in it.</li>
</ul>

Better noindex

Warns the author or admin in case of <meta name="robots" content="noindex"> hidden in a post.

room34

This plugin is an add-on for Modern Tribe’s The Events Calendar plugin. It adds a “noindex” meta tag to the individual detail pages for events after their end date has passed, to prevent them from appearing in search engines like Google or Bing.
Note that this only takes effect the next time a search engine indexes your site, so past events may still appear in search results for a few days.

noindex Past Events for The Events Calendar

Automatically add a "noindex" meta tag to The Events Calendar's detail pages for past events, to prevent them from appearing in search engines.

Better noindex vs noindex Past Events for The Events Calendar