Manipulate what post statuses are included in the SearchWP index and for searches to a single supplemental search engine

gistfile1.php

<?php
 
function my_searchwp_post_statuses( $post_status, $engine ) {
    
    $limited_post_status = array( 'publish' );
    $additional_post_status = array( 'publish', 'private' );
    
    if( is_null( $engine ) ) {
        // this is the indexer running, so we want to index our additional content
        $post_status = $additional_post_status;
    } else {
        // a search is taking place, but we only want to expose
        // additional content if it's the my_supplemental_search search engine
        if( 'my_supplemental_search' == $engine ) {
            $post_status = $additional_post_status;
        } else {
            // this is a search that is NOT using the my_supplemental_search search engine
            $post_status = $limited_post_status;
        }
    }
    
	return $post_status;
}
 
add_filter( 'searchwp_post_statuses', 'my_searchwp_post_statuses', 10, 2 );