Maybe I’m missing something, or just going bogeyed with fatigue. The select form helper allows you to add multiple as a custom attribute to turn it into a multi-select, but I don’t see a way of an array of values being recognises during parsing that will display them again once saved.

This is the code for the product-edit template

        $usage_hire_value = (array)get_post_meta( $object_id, '_wcv_custom_product_usage_hire', true );
        print_r( $usage_hire_value );

        $usage_hire_attributes = array( 'multiple' => 'multiple' );
        $usage_hire_options = array (  
            'holiday'   => __( 'Holiday Hire', 'wcvendors-pro' ),  
            'wedding'   => __( 'Wedding Hire', 'wcvendors-pro' ),  
            'prom'      => __( 'Prom & Ball Hire', 'wcvendors-pro' )
       	); 

        WCVendors_Pro_Form_Helper::select( apply_filters( 'wcv_custom_product_usage_hire', array( 
			'post_id'			=> $object_id, 
			'id' 				=> '_wcv_custom_product_usage_hire[]', 
			'label' 			=> __( 'What can I do?', 'wcvendors-pro' ), 
			'wrapper_start' 	=> '<div class="all-100">',
			'wrapper_end' 		=> '</div>', 
            'options' 			=> $usage_hire_options,
            'custom_attributes' => $usage_hire_attributes, 
            'value'             => $usage_hire_value
			) )
        );

and capturing the result via the save meta hook.

add_action( 'wcv_save_product_meta', 'riv_pro_save_product_meta', 10, 1 );
function riv_pro_save_product_meta ( $product_id ) {

    // product meta - usage hire
    if ( isset( $_POST[ '_wcv_custom_product_usage_hire' ] ) ) { 

		$usage_hire = $_POST[ '_wcv_custom_product_usage_hire' ];
        print_r( $usage_hire);

	    if ( ! empty( $usage_hire ) ) {
            foreach ( $usage_hire as $hire ) { $hire = wc_clean( $hire ); }
            update_post_meta( $product_id, '_wcv_custom_product_usage_hire', $usage_hire );    
		} else {
           delete_post_meta( $product_id, '_wcv_custom_product_usage_hire' );    
		}
    }    
}

A bit clunky atm but works. But… when reloading the page the meta is retrieved as an array but the select wont parse it as such. Is there a better way of doing this and still have the ability to multi select from a list?

Thanks