Use searchwp_custom_field_keys in SearchWP to customize the Custom Fields listed on the Settings screen

gistfile1.php

<?php
function mySwpCustomFields( $keys ) {
  // $keys is an array of Custom Field keys

  // I want to add 'sku' to that list
  $keys[] = 'sku';

  // I need to return my customized array back to SearchWP
  return $keys;
}

add_filter( 'searchwp_custom_field_keys', 'mySwpCustomFields' );