Modified class-wc-bookings-create.php - it saves the manually created order after adding the item meta

class-wc-bookings-create.php

<?php
/**
 * Create new bookings page.
 */
class WC_Bookings_Create {

	/**
	 * Stores errors.
	 *
	 * @var array
	 */
	private $errors = array();

	/**
	 * Output the form.
	 *
	 * @version  1.10.7
	 */
	public function output() {
		$this->errors = array();
		$step         = 1;

		try {
			if ( ! empty( $_POST ) && ! check_admin_referer( 'create_booking_notification' ) ) {
				throw new Exception( __( 'Error - please try again', 'woocommerce-bookings' ) );
			}

			if ( ! empty( $_POST['create_booking'] ) ) {
				$customer_id         = isset( $_POST['customer_id'] ) ? absint( $_POST['customer_id'] ) : 0;
				$bookable_product_id = absint( $_POST['bookable_product_id'] );
				$booking_order       = wc_clean( $_POST['booking_order'] );

				if ( ! $bookable_product_id ) {
					throw new Exception( __( 'Please choose a bookable product', 'woocommerce-bookings' ) );
				}

				if ( 'existing' === $booking_order ) {

					if ( class_exists( 'WC_Seq_Order_Number_Pro' ) ) {
						$order_id = WC_Seq_Order_Number_Pro::find_order_by_order_number( wc_clean( $_POST['booking_order_id'] ) );
					} else {
						$order_id = absint( $_POST['booking_order_id'] );
					}

					$booking_order = $order_id;

					if ( ! $booking_order || ! WC_Booking_Order_Compat::is_shop_order( $booking_order ) ) {
						throw new Exception( __( 'Invalid order ID provided', 'woocommerce-bookings' ) );
					}
				}

				$step ++;
				$product      = wc_get_product( $bookable_product_id );
				$booking_form = new WC_Booking_Form( $product );

			} elseif ( ! empty( $_POST['create_booking_2'] ) ) {
				$customer_id         = absint( $_POST['customer_id'] );
				$bookable_product_id = absint( $_POST['bookable_product_id'] );
				$booking_order       = wc_clean( $_POST['booking_order'] );
				$product             = wc_get_product( $bookable_product_id );
				$booking_data        = wc_bookings_get_posted_data( $_POST, $product );
				$cost                = WC_Bookings_Cost_Calculation::calculate_booking_cost( $booking_data, $product );
				$booking_cost        = $cost && ! is_wp_error( $cost ) ? number_format( $cost, 2, '.', '' ) : 0;
				$create_order        = false;
				$order_id            = 0;
				$item_id             = 0;

				if ( wc_prices_include_tax() ) {
					$base_tax_rates = WC_Tax::get_base_tax_rates( $product->get_tax_class() );
					$base_taxes     = WC_Tax::calc_tax( $booking_cost, $base_tax_rates, true );
					$booking_cost   = $booking_cost - array_sum( $base_taxes );
				}

				$props = array(
					'customer_id'   => $customer_id,
					'product_id'    => is_callable( array( $product, 'get_id' ) ) ? $product->get_id() : $product->id,
					'resource_id'   => isset( $booking_data['_resource_id'] ) ? $booking_data['_resource_id'] : '',
					'person_counts' => $booking_data['_persons'],
					'cost'          => $booking_cost,
					'start'         => $booking_data['_start_date'],
					'end'           => $booking_data['_end_date'],
					'all_day'       => $booking_data['_all_day'] ? true : false,
				);

				if ( 'new' === $booking_order ) {
					$create_order = true;
					$order_id     = $this->create_order( $booking_cost, $customer_id );

					if ( ! $order_id ) {
						throw new Exception( __( 'Error: Could not create order', 'woocommerce-bookings' ) );
					}
				} elseif ( $booking_order > 0 ) {
					$order_id = absint( $booking_order );

					if ( ! $order_id || ! WC_Booking_Order_Compat::is_shop_order( $order_id ) ) {
						throw new Exception( __( 'Invalid order ID provided', 'woocommerce-bookings' ) );
					}

					$order = new WC_Order( $order_id );

					$order->set_total( $order->get_total( 'edit' ) + $booking_cost );
					$order->save();

					do_action( 'woocommerce_bookings_create_booking_page_add_order_item', $order_id );
				}

				if ( $order_id ) {
					$order = wc_get_order( $order_id );
					$item_id = wc_add_order_item(
						$order_id,
						array(
							'order_item_name' => $product->get_title(),
							'order_item_type' => 'line_item',
						)
					);

					if ( ! $item_id ) {
						throw new Exception( __( 'Error: Could not create item', 'woocommerce-bookings' ) );
					}

					if ( ! empty( $customer_id ) ) {
						$keys  = array(
							'first_name',
							'last_name',
							'company',
							'address_1',
							'address_2',
							'city',
							'state',
							'postcode',
							'country',
							'phone',
						);
						$types = $product->is_virtual() ?
							array( 'billing' ) :
							array( 'shipping', 'billing' );

						foreach ( $types as $type ) {
							foreach ( $keys as $key ) {
								$value = (string) get_user_meta( $customer_id, $type . '_' . $key, true );
								$order->update_meta_data( '_' . $type . '_' . $key, $value );
							}
						}
					} 

					// Add line item meta
					wc_add_order_item_meta( $item_id, '_qty', 1 );
					wc_add_order_item_meta( $item_id, '_tax_class', $product->get_tax_class() );
					wc_add_order_item_meta( $item_id, '_product_id', $product->get_id() );
					wc_add_order_item_meta( $item_id, '_variation_id', '' );
					wc_add_order_item_meta( $item_id, '_line_subtotal', $booking_cost );
					wc_add_order_item_meta( $item_id, '_line_total', $booking_cost );
					wc_add_order_item_meta( $item_id, '_line_tax', 0 );
					wc_add_order_item_meta( $item_id, '_line_subtotal_tax', 0 );

					$order->save();
					
					do_action( 'woocommerce_bookings_create_booking_page_add_order_item', $order_id );
				
					
				}
				// Calculate the order totals with taxes.
				$order = wc_get_order( $order_id );
				if ( is_a( $order, 'WC_Order' ) ) {
					$order->calculate_totals( wc_tax_enabled() );
				}

				// Create the booking itself
				$new_booking = new WC_Booking( $props );
				$new_booking->set_order_id( $order_id );
				$new_booking->set_order_item_id( $item_id );
				$new_booking->set_status( $create_order ? 'unpaid' : 'confirmed' );
				$new_booking->save();

				do_action( 'woocommerce_bookings_created_manual_booking', $new_booking );

				$redirect_url = $create_order
					? $order->get_edit_order_url()
					: admin_url( 'post.php?post=' . $new_booking->get_id() . '&action=edit' );

				wp_safe_redirect( $redirect_url );
				exit;

			}
		} catch ( Exception $e ) {
			$this->errors[] = $e->getMessage();
		}

		switch ( $step ) {
			case 1:
				include 'views/html-create-booking-page.php';
				break;
			case 2:
				add_filter( 'wc_get_template', array( $this, 'use_default_form_template' ), 10, 5 );
				include 'views/html-create-booking-page-2.php';
				remove_filter( 'wc_get_template', array( $this, 'use_default_form_template' ), 10 );
				break;
		}
	}

	/**
	 * Create order.
	 *
	 * @param  float $total
	 * @param  int   $customer_id
	 * @return int
	 */
	public function create_order( $total, $customer_id ) {
		$order = new WC_Order();
		$order->set_customer_id( $customer_id );
		$order->set_total( $total );
		$order->set_created_via( 'bookings' );
		$order_id = $order->save();

		do_action( 'woocommerce_new_booking_order', $order_id );

		return $order_id;
	}

	/**
	 * Output any errors
	 */
	public function show_errors() {
		foreach ( $this->errors as $error ) {
			echo '<div class="error"><p>' . esc_html( $error ) . '</p></div>';
		}
	}

	/**
	 * Use default template form from the extension.
	 *
	 * This prevents any overridden template via theme being used in
	 * create booking screen.
	 *
	 * @since 1.9.11
	 * @see https://github.com/woothemes/woocommerce-bookings/issues/773
	 */
	public function use_default_form_template( $located, $template_name, $args, $template_path, $default_path ) {
		if ( 'woocommerce-bookings' === $template_path ) {
			$located = $default_path . $template_name;
		}
		return $located;
	}
}