Use this script to copy customization from parent theme

copy_parent_theme_mods.php

<?php
/**
 * This script just need to run once
 * You can remove this script after the copy completed
 */
function copy_parent_mods(){
  $parent_mods = get_option( 'theme_mods_' . get_template() );
  foreach ( (array) $parent_mods as $parent_mod => $parent_mod_value ) {
    set_theme_mod( $parent_mod, $parent_mod_value );
  }
}
add_action( 'init', 'copy_parent_mods' );