WordPress at a glance
filter is not described

wp_super_cache_supercachedir filter-hook . WPSCache 1.0

Usage

add_filter( 'wp_super_cache_supercachedir', 'filter_function_name_2623' );
function filter_function_name_2623( $cache_path . 'supercache/' . trailingslashit ){
	// filter...

	return $cache_path . 'supercache/' . trailingslashit;
}
$cache_path . 'supercache/' . trailingslashit
-

Where the hook is called

get_supercache_dir()
wp_super_cache_supercachedir
wp-super-cache/wp-cache-phase2.php 619
return trailingslashit( apply_filters( 'wp_super_cache_supercachedir', $cache_path . 'supercache/' . trailingslashit( strtolower( preg_replace( '/:.*$/', '', str_replace( 'http://', '', str_replace( 'https://', '', $home ) ) ) ) ) ) );

Where in WP core the hook is used WP Super Cache

wp-super-cache/plugins/domain-mapping.php 56
add_filter( 'wp_super_cache_supercachedir', 'domain_mapping_supercachedir' );