You can now configure a certain model so that you are not forced to insert content for every language your administrative area supports, but just for the primary one, and then manually add additional locales on a per-record basis.
This allows use cases such as multi-language blogs, where some articles can be written only in English, other only in Italian and others in both languages.
You can enable optional translations in your Model settings:
This will be the result for the editor:
