PageProperties allows to easily edit display title, language and content model of a page. To associate semantic properties to pages without to manually annotate them (provided that Semantic MediaWiki is installed), and to set arbitrary SEO meta tags for the entire wiki or specific pages.
Since version 1.2 it also offers a complete GUI for the creation of semantic forms and the creation of articles or editing of semantic properties through them.
Please check https://www.mediawiki.org/wiki/Extension:PageProperties for the official documentation.