Custom HTML

import Screenshots from '@site/src/components/Screenshots';
The custom HTML field allows you to output anything. You can even use a PHP callback function to output the HTML.
This field is usually used to display custom messages/instructions to users. Sometimes, it's used with PHP callback to display more advanced content (such as content from a query).
Screenshots
<Screenshots name="custom-html" col1={[
['https://imgur.elightup.com/LO5Akul.png', 'The custom HTML field interface']
]} />
Settings
Besides the common settings, this field has the following specific settings, the keys are for use with code:
Name
Key
Description
Content
std
The custom HTML content.
PHP Callback
callback
The PHP function that returns the custom HTML content. Optional.
This is a sample field settings array for registering this field with code:
[
    'type' => 'custom_html',
    'std'  => '<div class="alert alert-warning">This is a custom HTML content</div>',
],
Styling
Because this field is usually used to display custom content, it requires some CSS to make the content looks good. To enqueue a CSS file to the admin editing page, use the rwmb_enqueue_scripts hook:
add_action( 'rwmb_enqueue_scripts', function () {
    wp_enqueue_style( 'style-id', get_template_directory_uri() . '/css/admin.css' );
} );
And in the 
admin.css you can put your custom styles.