Custom CSS, Javascript and HTML on specific posts or page or you can do it in global.
You can insert them in Header or Footer.
Features
Text editor with syntax highlighting
Code validation
Inlined CSS AND JS
Custom CSS and Javascript on specific post or global
Custom HTML before|after body tag and footer specific post or global
Theme Editor Preference
Shortcode contents supported
Installation
Go to Plugins > Add New > WP Css, Javascript and HTML
Go to Settings > WP Css, Javascript and HTML
To enable this feature on specific post you must click the tree dots > Preferences > Panels > Enable CSS, Javascript and HTML or click here for visual.