Exclude events from event lists using a tag. In this example, any events with the tag "exclude" will not be included in front end event lists. Event Espresso 4.

exclude_events.php

<?php // only add this opening PHP tag if starting with a new file with no opening PHP tag

add_filter( 'posts_where', 'ee_remove_hidden_tagged_event_list', 25, 2 );
function ee_remove_hidden_tagged_event_list( $SQL, WP_Query $wp_query ) {
    global $wpdb;
    $tag = get_term_by( 'slug', 'exclude', 'post_tag' );
    if( $tag instanceof WP_Term ) {
      $tag_id = $tag->term_id;
    } else {
      return $SQL;
    }
    if ( 
        isset( $wp_query->query_vars['post_type'] ) && 
        ( $wp_query->query_vars['post_type'] == 'espresso_events'  ||
        ( is_array( $wp_query->query_vars['post_type'] ) && 
        in_array( 'espresso_events', $wp_query->query_vars['post_type'] ) ) ) &&
        ! $wp_query->is_singular ) {
            $SQL .= " AND ID NOT IN (SELECT object_id FROM {$wpdb->term_relationships} WHERE term_taxonomy_id={$tag_id} )"; // change to hidden tag ID
    }
    return $SQL;
}