Is there a visual editor specifically for page snippets/sections?

I found that this can be done simply by using WordPress’ Page editor. Nothing else is needed:

1. Compose the content in WordPress’ Page editor
2. Save (but don’t publish)
3. In your code, retrieve the saved content

By ID:

$id=47;
$post = get_post($id);
$content = apply_filters('the_content', $post->post_content); 
echo $content;

Or by page title:

$title="page title";
$page = get_page_by_title( $title );
$content = apply_filters('the_content', $page->post_content); 
echo $content;

Note that apply_filters is used in case there is a plugin somewhere that wants to “apply filters” to the_content – it’s good for forwards compatibility.