Add the invited person's email address to the Group Account invite link.

my_pmprogroupacct_invite_link_add_invited_email.php

<?php
/*
 * Add the invited person's email address to the Group Account invite link.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmprogroupacct_invite_link_add_invited_email( $data, $email ) {

	if ( 'pmprogroupacct_invite' === $email->template ) {
		$data['pmprogroupacct_invite_link'] = esc_url( add_query_arg( 'invited-email', $email->email, $data['pmprogroupacct_invite_link'] ) );
	}

	return $data;
}
add_filter( 'pmpro_email_data', 'my_pmprogroupacct_invite_link_add_invited_email', 10, 2 );