[Support request] Excluded posts still appear

I’m not exactly sure if this will fit what you’re looking for but try this code:

add_filter('post_link', 'track_displayed_posts');
add_action('pre_get_posts','remove_already_displayed_posts');
 
$displayed_posts = [];
 
function track_displayed_posts($url) {
  global $displayed_posts;
  $displayed_posts[] = get_the_ID();
  return $url; // don't mess with the url
}
 
function remove_already_displayed_posts($query) {
 global $displayed_posts;
 $query->set('post__not_in', $displayed_posts);
}

This particular code removes existing posts on the other list if it exists on the one list.