Maštarija

Do you often need to create small pieces of content that should be present on e.g. every product page, but don’t justify writing a full on plugin?
Do you mostly work with designers or users that sometimes need to update some of that content, but they don’t know their way through Git, FTP or code in general?
If you’ve answered yes to any of those two questions then this plugin is for you!
Heckler allows you to create reusable pieces of code or text and execute / display them on any wordpress hook (after <code>init</code>) or use them as a simple shortcode within your content.
If you have some coding skills, you can programm a rule which determines if the text should be shown, or the code should be hooked or executed.
As an added bonus, there’s even a VIM mode in the code editor to make your life as a developer in this world of makeshift plugins just a little more bearable.
If you wish to contribute to this wonderfully horrible plugin you can do so on its <a href="https://github.com/mastarija/heckler" rel="nofollow ugc">GitHub repository</a>.

Heckler

Create custom text and code snippets, and attach them to hooks or use them as short codes, along with programmable display rules.

Makoto

This plugin allows you to insert html code into <a href="https://wordpress.org/extend/themes/mystique" rel="ugc">Mystique theme</a> without the need to hand code the original theme files.
This plugin will enable you to insert html code in the header and footer area. 
This plugin also will enable you to insert code into above your post and after your post content.

Guan Mystique Theme Code Inserter

This plugin allows you to insert html code into Mystique theme without the need to hand code the original theme files.

Heckler vs Guan Mystique Theme Code Inserter