There isn't any way currently to easily identify missing translations for Sections and Categories.

With help articles, you can easily identify missing translations using the Not translated to filter.

This isn't possible with Sections and Categories, and what's worse is that you can have articles translated to a language that won't be visible to end-users at all because the Section or Category they're in isn't translated to that language, but there isn't any indication that the translation is missing.

We recently launched ZD Guide to our German clients, and there are entire sections of articles missing because of missing translations. We now need to go through each category and section one-by-one to make sure everything is translated, which is an absolute pain.