WP Add Custom CSS的作者是Daniele De Santis,目前有100,000+个有效安装。已经Tested with 5.2.6版本的wordpress。
WP Add Custom CSS allows you to add custom CSS to the whole website and to individual posts, pages and custom post types (such as Woocommerce products).
The CSS rules applied to the whole website will override the default stylesheets of your theme and plugins, while the CSS rules applied to specific pages, posts or custom post types will override the main stylesheet too.
You can edit the main stylesheet from the the “Add custom CSS” settings page.
The plugin also creates a new “Custom CSS” box in the editing area to add custom CSS to specific posts, pages and custom post types.
Available languages:

German – thanks to Bodo Graumann
Spanish – thanks to Dave Krul