Apply CodeMirror
Applying CodeMirror enables smooth code editing in the editor's "Source View".
<table> <thead> <tr><th>'Source View' without CodeMirror applied</th><th>'Source View' with CodeMirror applied</th></tr> </thead> <tbody> <tr> <td>

You can apply CodeMirror by downloading the js and css files from the Code Mirror site and adding paths to them, or by using a CDN.
Alternatively, you can use the codemirror script files included in the externals directory of the Synap Editor package.
How to Apply
Using codemirror.min.js and xml.min.js included in externals/codeMirror
<!-- index.html -->
<!-- code mirror -->
<script type="text/javascript" src="externals/codeMirror/codemirror.min.js"></script>
<script type="text/javascript" src="externals/codeMirror/xml.min.js"></script>
<link rel="stylesheet" href="externals/codeMirror/codemirror.min.css">
Applying via CDN
Add the following to the <head> tag of the html file where the editor is installed.
<!-- index.html -->
<!-- code mirror -->
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.0/codemirror.min.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.0/mode/xml/xml.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.39.0/codemirror.min.css">