Translations:Help:Extension:Translate/Page translation administration/44/en

This option is not yet supported out of the box by the Translate extension. You need to either instruct your translators to add the language code suffix to the category markup in the translation, or leave the category out of translation and write your own templates which add the language code automatically. There are some such templates available on the wikis which use the Translate extension, but they won't be dealt with here. Translated categories' description pages still have to be created.