Add custom admin sortable columns

admin_columns.php

<?php

add_filter( 'manage_edit-resident_columns', 'set_custom_edit_resident_columns' );
add_action( 'manage_resident_posts_custom_column' , 'custom_resident_column', 10, 2 );

function set_custom_edit_resident_columns($columns) {
	$columns = array(
		'cb'	 	=> '<input type="checkbox" />',
		'title' 	=> 'Title',
		'display'	=> 'Display',
	);
	return $columns;
}

function custom_resident_column( $column, $post_id ) {
	if ( $column == 'display') {

		if ( '1' == get_field('res_display', $post_id) ) {
			echo 'Yes';
		} else {
			echo 'No';
		}

	}

}
//* Make column sortable
add_filter("manage_edit-resident_sortable_columns", "bhl_column_register_sortable" );
function bhl_column_register_sortable( $columns )
{
	$columns['display'] = 'display';
	return $columns;
}

//* Do the sorting
add_action( 'pre_get_posts', 'bhl_order_classes' );
function bhl_order_classes( $query ) {

        $post_type = $query->get('post_type');

        // If resident cpt
        if ( $post_type == 'resident' ) {

        	// If set to short by res_display custom field
            if ( $query->get( 'orderby' ) == 'display' ) {

                $query->set('meta_key','res_display');
				$query->set('orderby','meta_value_num');

  			} elseif ( $query->get( 'orderby' ) == '' ) {

                $query->set( 'orderby', 'title' );

   			}
            /* Post Order: ASC / DESC */
            if( $query->get( 'order' ) == '' ){
                $query->set( 'order', 'ASC' );
            }
        }

}