https://en.support.wordpress.com/shortcodes/
https://codex.wordpress.org/Shortcode
Examples of Shortcodes for Contact Forms
Please note, trying to get WordPress to format the ShortCode as Code was a futile gesture. I consistently changed my html entities back into code points and removed my code html designation.
Showing it as a picture is lame; however, I will be researching how to accomplish this. WordPress can do some funny things with the editor. Search for "wordpress editor problems". I think I might link to outside pages for code. I can control what happens in plain html and css. I can't always control what WordPress does.