Далее зайдите в Редактор шаблонов-->Другие шаблоны-->Экспорт товаров в Яндекс.Маркет и найдите:
<description><![CDATA[{% IF SHOP_OFFER_DESC_TYPE=1%}{% IF SHOP_OFFER_FILTER_HTML=2 %}{goods.DESCRIPTION_SHORT}{% ELSE%}{goods.DESCRIPTION_SHORT}{% ENDIF %}{% ELSEIF SHOP_OFFER_DESC_TYPE=2%}{% IF SHOP_OFFER_FILTER_HTML=2 %}{goods.DESCRIPTION_LARGE}{% ELSE%}{goods.DESCRIPTION_LARGE | strip_tags}{% ENDIF %}{% ELSEIF SHOP_OFFER_DESC_TYPE=3%}{% IF goods.DESCRIPTION_SHORT %}{% IF SHOP_OFFER_FILTER_HTML=2 %}{goods.DESCRIPTION_SHORT}{% ELSE%}{goods.DESCRIPTION_SHORT}{% ENDIF %}{% ELSE %}{% IF SHOP_OFFER_FILTER_HTML=2 %}{goods.DESCRIPTION_LARGE}>{% ELSE%}{goods.DESCRIPTION_LARGE | strip_tags}{% ENDIF %}{% ENDIF %}{% ELSEIF SHOP_OFFER_DESC_TYPE=4%}{% IF goods.DESCRIPTION_LARGE %}{% IF SHOP_OFFER_FILTER_HTML=2 %}{goods.DESCRIPTION_LARGE}{% ELSE%}{goods.DESCRIPTION_LARGE | strip_tags}{% ENDIF %}{% ELSE %}{% IF SHOP_OFFER_FILTER_HTML=2 %}{goods.DESCRIPTION_SHORT}{% ELSE%}{goods.DESCRIPTION_SHORT}{% ENDIF %}{% ENDIF %}{% ENDIF %}]]></description>
после него вставьте:
{% FOR attr %}{% IF goods.attr.NAME=Уценка %} <condition type="likenew"> <reason>{goods.attr.VALUE}</reason> </condition> {break}{%ENDIF%} {% ENDFOR %}