Drupal 8: Admin override of first item in a view

OverrideViewFirstItem.php

<?php

use Drupal\views\ViewExecutable;
use Drupal\views\Plugin\views\query\QueryPluginBase;

/**
 * @file
 * Hooks and procedural code for My Module
 *
 * This code should be in a *.module or *.inc file
 */

/**
 * Implements hook_views_query_alter()
 */
function my_module_views_query_alter(ViewExecutable $view, QueryPluginBase $query) {
  // Alter my_view query depending on input to the Featured Nodes form.
  if ($view->id() === 'my_view') {
    // Get config.
    $config = \Drupal::config('my_module.featured_node');
    if (is_object($config) && !empty($config->get('featured_node'))) {
      // Add WHERE to query.
      $nid = $config->get('featured_node');
      // If featured block, view nid should be the admin-set view.
      if (!empty($insight_view_featured) && $view->getDisplay()->display['id'] == 'featured_display') {
        $operator = '=';
      }
      // If general landing page ...
        // ... view nid should NOT be the admin-set view,
        // and set offset to 0.
      elseif (!empty($insight_view_page) && $view->getDisplay()->display['id'] == 'list_display') {
        $operator = '<>';
        $view->setOffset(0);
      }
      $query->addWhere(1, 'node_field_data.nid', $nid, $operator);
    }
  }
}