WP HTML Block
WP HTML Block help you to create HTML Block so that you can insert it to any place like page, post, custom post type, widget etc via shortcode or a button in the TinyMCE visual editor toolbar.
As per your need, you can reuse/modify the output of a shortcode via a hook so that you can change a wrapper, class etc. WP HTML Block provides you a really simple way to add third pary code like PayPal donation buttons, iFrames etc. You will get separate shortcode for each HTML Block you create.