The filter is being used to add specific options to the ignore list, to be allowed for save separately, within each of the domains.
The following example adds to the ignore the theme_settings option name:

    add_filter( 'woomd/ignore_options',     'WooMD_ignore_options');
    function  WooMD_ignore_options ( $ignore_options )
        {
            $ignore_options[] = 'theme_settings';
             
            return $ignore_options;   
        }

A global match can be achieved for an option using the % symbol, the following example will match all options like theme_color, theme_style, theme_layout etc:

    add_filter( 'woomd/ignore_options',     'WooMD_ignore_options');
    function  WooMD_ignore_options ( $ignore_options )
        {
            $ignore_options[] = 'theme_%';
             
            return $ignore_options;   
        }

The code should be placed inside a php file on wp-content/mu-plugins/ folder.

The filter is being used to change the $checkout_url for specific shops. As default this is being controlled through admin settings but can be adjusted to particular shops if need.
The following code change the checkout url to shop default when blog_id is 4:

    add_filter( 'woomd/get_checkout_url',     'WooMD_get_checkout_url');
    function  WooMD_get_checkout_url ( $checkout_url )
        {
            global $blog_id;

            if( $blog_id == 4 )
                {
                    $_checkout_url = wc_get_page_permalink( 'checkout' );
                    if ( $_checkout_url ) 
                        {
                            // Force SSL if needed
                            if ( is_ssl() || 'yes' === get_option( 'woocommerce_force_ssl_checkout' ) ) 
                                {
                                    $checkout_url = str_replace( 'http:', 'https:', $checkout_url );
                                }
                        }    
                }
             
            return $checkout_url;   
        }

The code should be placed inside a php file on wp-content/mu-plugins folder or theme functions.php.

Filter being used to acknowledge the plugin engine to proceed with synchronization, usually following a custom AJAX call which is not being recognized as a WooCommerce default. (e.g. wc-ajax=add_to_cart,  wc-ajax=get_refreshed_fragments)

Certain plugins and themes use their own methods to handle the cart operations like add, remove.  To create a compatibility between such code and the WooCommerce Global Cart plugin, at least a POST parameter must be registered through the ‘woomd/sync/on_post_vars’ filter, recommended to be a unique field. The following sample code, inform the plugin engine to trigger a synchronization procedure right after a POST call has completed and included a field action => woocommerce_add_to_cart_variable_rc

Sample Usage

add_filter('woomd/sync/on_post_vars', 'woomd_sync_on_post_vars');
function woomd_sync_on_post_vars( $PostVars )
    {
        $PostVars[] = 'action=add_to_cart';
        $PostVars[] = 'action=woocommerce_add_to_cart_variable_rc';
        $PostVars[] = 'action=product_remove';

        return $PostVars ;
    }

The filter is being used to disable the Global Cart functionality. The Global Cart works as a unique cart for all shops in the MultiSite Network, a product pushed to the cart will be show on all other shops too.

    add_filter( 'woomd/disable_global_cart',     'WooMD_Disable_GlobalCart', 10, 2 );
    function  WooMD_Disable_GlobalCart ( $status, $_blog_id = '' )
        {
            
            return TRUE;   
        }

The code should be placed inside a php file on wp-content/mu-plugins folder.

The Global Cart can be disabled for individual sites, the following code can be used, in this example, the 3 and 4 are the sites ID that will be disabled:

    define ( 'WooMD_GC_Ignore_Sites', array( 3, 4 ) );
       
    
    add_filter( 'woomd/disable_global_cart',     'WooMD_Disable_GlobalCart');
    function  WooMD_Disable_GlobalCart ( $status, $_blog_id = '' )
        {
            
            global $blog_id;
            
            if ( empty ( $_blog_id ) )
                $_blog_id    =   $blog_id;
            
            if (  in_array( $_blog_id, WooMD_GC_Ignore_Sites ))
                return TRUE;   
                
            return $status;
            
        }