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.

Patryk

The plugin adds a “noindex” field in the edit window for pages, posts and custom post types (CPT), which, when selected – after saving, adds the “noindex” tag to a given page. The tag blocks the indexing of a given page in search engines, e.g. Google.

PRyC WP: Add noindex tag

The plugin adds a "noindex" field in the edit window for pages, posts and custom post types (CPT), which, when selected - after saving, adds …

Better noindex vs PRyC WP: Add noindex tag