Topic on Help talk:Extension:Translate

Solution was given via Translator's noticeboard: just reformat the categories on the base-page (not any of the translated pages) from [[Category:CatName]] to [[Category:CatName{{#if:{{#translation:}}|/Translations}}]]

See meta:Community Wishlist/Wishes/Enable subcategorizing translated pages on Commons. I think that's currently not possible but if it is, users can't do so and it's not done automatically.

The Translate extension does not handle categories in a special way. That's why we have left it up to translation admins to decide whether they want all translations to be in one category or in separate language categories and this is reflected in our documentation: Help:Extension:Translate/Page translation administration#Markup examples.

This might change a little in the future if https://phabricator.wikimedia.org/T285463 gets implemented.