Meta:Extensions Wishlist

TemplateData: https://www.mediawiki.org/wiki/Extension:TemplateData allows building UX for templates in the normal editor (like having fields for title and things like that)

ParserFunctions: https://www.mediawiki.org/wiki/Extension:ParserFunctions: Used in multiple templates and can be used to embed html

TemplateStyles: https://www.mediawiki.org/wiki/Extension:TemplateStyles allows styles that apply to a specific template. Used in the documentation pages eg Template:Infobox/doc

SyntaxHighlight: https://www.mediawiki.org/wiki/Extension:SyntaxHighlight for documentation pages, low priority