How do I set up the Rich Text Editor Field (Redactor) for code snippets?
Not sure if it helps, but I accomplished this using a plain text field (with multi-line enabled). Then I just used CSS to format the field in a way to make it look like a code snippet...

Screenshot of field in the Control Panel:



I used the Control Panel CSS plugin to add this CSS:

#fields-myfieldhandle textarea.nicetext {
    font-size: 13px;
    font-family: Menlo, Monaco, monospace, sans-serif;
    color: #cccccc;
    background-color: #222222;
    padding: 14px 16px;
}


Then, in my Twig template, I display it like this:

&lt;pre&gt;&lt;code&gt;{{ block.code|e }}&lt;/code&gt;&lt;/pre&gt;


May or may not be the solution you're looking for, but I've been very satisfied with it!