mypmpro-show-customer-id-field.php

<?php
// Make all fields editable on the orders page in the PMPro dashboard
add_filter( 'pmpro_orders_read_only_fields', function( $fields ) {
	return array();
} );

/**
 * Register the Stripe Customer ID field for admin profiles
 */
function my_pmpro_add_stripe_customerid_field() {

	// Ensure PMPro_Field class exists (PMPro 2.11+)
	if ( ! class_exists( 'PMPro_Field' ) ) {
		return;
	}

	// Don't load at checkout
	if ( ! empty( $_REQUEST['pmpro_level'] ) ) {
		return;
	}

	$fields = array();

	// Define the field
	$fields[] = new PMPro_Field(
		'pmpro_stripe_customerid', // meta key
		'text',                    // field type
		array(
			'label'       => 'Stripe Customer ID',
			'size'        => 40,
			'profile'     => 'admins', // visible to admins only
			'memberslistcsv' => false, // exclude from CSV exports
			'required'    => false,
			'profile'	 => 'only_admin',
		)
	);

	// Add field to the profile section (admin side)
	// Add all of our fields into that group.
	foreach ( $fields as $field ) {
		pmpro_add_user_field(
			'More Information',		// Which group to add to.
			$field					// PMPro_Field object
		);
	}
}
add_action( 'init', 'my_pmpro_add_stripe_customerid_field' );