Add 'Awaiting pre-order' custom status to WooCommerce with bulk edit and custom status color

functions.php

<?php // Don't copy this line

/** 
 * Add 'Awaiting pre-order' custom status
 * 
 * 1. Register new order status
 * 2. Add to list of WC order statuses
 * 3. Add your custom bulk action in dropdown 
 * 4. Bulk action handler
 * 5. Admin notices for bulk action
 * 6. Style the status in the orders list
 * 
 * CREDITS
 * https://jilt.com/blog/woocommerce-custom-order-status-2/
 * https://rudrastyh.com/woocommerce/bulk-change-custom-order-status.html
 * https://stackoverflow.com/a/49341814
 */

/*
 * 1. Register new order status
 */
function aw_register_awaiting_preorder_order_status() {
    register_post_status( 'wc-awaiting-preorder', array(
        'label'                     => 'Awaiting pre-order',
        'public'                    => true,
        'exclude_from_search'       => false,
        'show_in_admin_all_list'    => true,
        'show_in_admin_status_list' => true,
        'label_count'               => _n_noop( 'Awaiting pre-order (%s)', 'Awaiting pre-order (%s)' )
    ) );
}
add_action( 'init', 'aw_register_awaiting_preorder_order_status' );

/*
 * 2. Add to list of WC order statuses
 */
function aw_add_awaiting_preorder_to_order_statuses( $order_statuses ) {
 
    $new_order_statuses = array();
 
    // add new order status after processing
    foreach ( $order_statuses as $key => $status ) {
 
        $new_order_statuses[ $key ] = $status;
 
        if ( 'wc-pending' === $key ) {
            $new_order_statuses['wc-awaiting-preorder'] = 'Awaiting pre-order';
        }
    }
 
    return $new_order_statuses;
}
add_filter( 'wc_order_statuses', 'aw_add_awaiting_preorder_to_order_statuses' );

/*
 * 3. Add your custom bulk action in dropdown
 */
add_filter( 'bulk_actions-edit-shop_order', 'aw_register_bulk_action' ); // edit-shop_order is the screen ID of the orders page
 
function aw_register_bulk_action( $bulk_actions ) {
 
	$bulk_actions['mark_awaiting_preorder'] = 'Mark awaiting pre-order'; // <option value="mark_awaiting_preorder">Mark awaiting pre-order</option>
	return $bulk_actions;
 
}
 
/*
 * 4. Bulk action handler
 * Make sure that "action name" in the hook is the same like the option value from the above function
 */
add_action( 'admin_action_mark_awaiting_preorder', 'aw_bulk_process_custom_status' ); // admin_action_{action name}
 
function aw_bulk_process_custom_status() {
 
	// if an array with order IDs is not presented, exit the function
	if( !isset( $_REQUEST['post'] ) && !is_array( $_REQUEST['post'] ) )
		return;
 
	foreach( $_REQUEST['post'] as $order_id ) {
 
		$order = new WC_Order( $order_id );
		$order_note = 'Order updated by admin:';
		$order->update_status( 'wc-awaiting-preorder', $order_note, true ); 
 
	}
 
	// of course using add_query_arg() is not required, you can build your URL inline
	$location = add_query_arg( array(
    	'post_type' => 'shop_order',
		'marked_awaiting_preorder' => 1, // marked_awaiting_preorder=1 is just the $_GET variable for notices
		'changed' => count( $_REQUEST['post'] ), // number of changed orders
		'ids' => join( $_REQUEST['post'], ',' ),
		'post_status' => 'all'
	), 'edit.php' );
 
	wp_redirect( admin_url( $location ) );
	exit;
 
}
 
/*
 * 5. Admin notices for bulk action
 */
add_action('admin_notices', 'aw_custom_order_status_notices');
 
function aw_custom_order_status_notices() {
 
	global $pagenow, $typenow;
 
	if( $typenow == 'shop_order' 
	 && $pagenow == 'edit.php'
	 && isset( $_REQUEST['marked_awaiting_preorder'] )
	 && $_REQUEST['marked_awaiting_preorder'] == 1
	 && isset( $_REQUEST['changed'] ) ) {
 
		$message = sprintf( _n( 'Order status changed.', '%s order statuses changed.', $_REQUEST['changed'] ), number_format_i18n( $_REQUEST['changed'] ) );
		echo "<div class=\"updated\"><p>{$message}</p></div>";
 
	}
 
}

/*
 * 6. Style the status in the orders list
 */
add_action('admin_head', 'aw_styling_admin_order_list' );
function aw_styling_admin_order_list() {
    global $pagenow, $post;

    if( $pagenow != 'edit.php') return; // Exit
    if( get_post_type($post->ID) != 'shop_order' ) return; // Exit

    // HERE we set your custom status
    $order_status = 'Dispatched'; // <==== HERE
    ?>
    <style>
        .order-status.status-awaiting-preorder {
            background: #334862;
            color: #fff;
        }
    </style>
    <?php
}