Przekopiowujemy plik z Core:
app/code/core/Mage/Catalog/Model/Category.php
do Local:
app/code/local/Mage/Catalog/Model/Category.php
i modyfikujemy tę część kodu (komentujemy):

Mage::getSingleton('index/indexer')->processEntityAction( $this, self::ENTITY, Mage_Index_Model_Event::TYPE_SAVE ); 
Mage::app()->cleanCache(array(self::CACHE_TAG));

na:

/*Mage::getSingleton('index/indexer')->processEntityAction( $this, self::ENTITY, Mage_Index_Model_Event::TYPE_SAVE ); 
Mage::app()->cleanCache(array(self::CACHE_TAG)); */