Meta Box

Thank you, its now working!

I solved it myself thank you, here is how I did it , for anyone else wishing to do this that has some level of skill but not a developer.

1. Created the Custom Field Types using the Metabox interface. Set them up exactly as I want, without the default value.
2. Clicked Get PHP Code and copied that code, minus the <?php tag into my functions.php
3. Added my PHP query to get the user details
`global $current_user;
get_currentuserinfo();
$user_name = $current_user->display_name;
$user_email = $current_user->user_email;
$user_first = $current_user->user_firstname;
$user_last = $current_user->user_lastname; `

4. added the 'std' => $user_name, etc etc to each field to show the correct variable
5. output the shortcode of the form <?php echo do_shortcode("[mb_frontend_form id='request-membership-status' ]") ?>
Job Done!!!
Here is the complete function I created so if anyone else wants to follow it they can see how it has to be set up as a working function for the MB Frontend Submission form.

add_filter( 'rwmb_meta_boxes', 'request_membership_status' );

function request_membership_status( $meta_boxes ) {
    $prefix = '';

    // your code to get the current user name here
	global $current_user;
	get_currentuserinfo();
    $user_name = $current_user->display_name;
	$user_email = $current_user->user_email;
	$user_first = $current_user->user_firstname;
	$user_last = $current_user->user_lastname;

    $meta_boxes[] = [
        'title'      => __( 'Request Membership Status', 'pinkequine-com' ),
        'id'         => 'request-membership-status',
        'post_types' => ['membership-request'],
        'fields'     => [
            [
                'name'          => __( 'First Name', 'pinkequine-com' ),
                'id'            => $prefix . 'user_first',
                'type'          => 'text',
                'admin_columns' => 'replace title',
                'std'			=> $user_first,
            ],
            [
                'name'          => __( 'Last Name', 'pinkequine-com' ),
                'id'            => $prefix . 'user_last',
                'type'          => 'text',
                'admin_columns' => 'after user_first',
				'std'			=> $user_last,
            ],
            [
                'name'          => __( 'Username', 'pinkequine-com' ),
                'id'            => $prefix . 'user_name',
                'type'          => 'text',
                'admin_columns' => 'after user_last',
				'std'			=> $user_name,
            ],
            [
                'name'          => __( 'Email', 'pinkequine-com' ),
                'id'            => $prefix . 'user_email',
                'type'          => 'text',
                'admin_columns' => 'after user_name',
				'std'			=> $user_email,
            ],
            [
                'name'              => __( 'Membership', 'pinkequine-com' ),
                'id'                => $prefix . 'checkbox_membership',
                'type'              => 'checkbox',
                'label_description' => __( 'Please add user Member to my profile', 'pinkequine-com' ),
                'required'          => true,
                'admin_columns'     => 'after user_email',
            ],
        ],
        'validation' => [
            'rules'    => [
                $prefix . 'checkbox_membership' => [
                    'required' => true,
                ],
            ],
            'messages' => [
                $prefix . 'checkbox_membership' => [
                    'required' => 'Please check the box to confirm your request',
                ],
            ],
        ],
    ];

    return $meta_boxes;
}

EDIT: I corrected a typo on the last 2 variables.

Here is how I am calling the form and that shows up exactly as expected
echo do_shortcode ("[mb_frontend_form id='request-membership-status' ]")

And here is one of the form fields to be populated with the variables
Screenshot

Thanks I did see that on the docs, but thought it was more of a general setting and I wondered about conflicts - e.g all user name fields as user_name that it would cause an issue in the post_meta table.

However, if I am understanding what you are saying is that I could have several fields e.g.user_name1, user_name2 etc and then declare them each in here with the same variable name in this case $user_name.

Thank you for this, I've literally read so much php/sass/jquery etc my eyes are going funny! Sometimes you can't see the wood, for the trees!

I see, I will probably have to make it a manual request for now then via email because I have am using the plugins USER ROLE EDITOR, YITH AFFILIATES and WOOCOMMERCE all of these add user roles to the main one.

Thank you for your consideration of this in future updates though.

Thank you that worked!

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly.
}

global $post;

$short_description = apply_filters( 'woocommerce_short_description', $post->post_excerpt );

    if ( ! $short_description )
        return;

    // Bullet Points
    $bullet_points = '<ul class="product__short-description--bullets">' .  rwmb_the_value( "product_bullet_point" ) . '</ul>';
    
    // The custom text
    $custom_text = '<ul class="product__short-description--bullets--red">
    <li>Please see our <a href="https://www.pinkequine.com/buyers-guide/">Buyers Guide</a> for current delivery times on Bespoke Products</li>
    </ul>';
      ?>
    
    <div class="product__short-description">
        <?php echo $short_description . $bullet_points . $custom_text ; // WPCS: XSS ok. ?>
    </div>