wcbvp_enable_variations_grid.php

<?php
/**
 * Display grid for logged-in users / standard layout for guests
 */
function demo_enable_variations_grid( $enable, $product_id  ) {
  if( is_user_logged_in() ) {
    return true;
  } else {
    return false;
  }
}
add_filter( 'wcbvp_enable_variations_grid', 'demo_enable_variations_grid', 10, 2 );