If you're an editor and writing ahead content in multiple languages, you may find this feature a real time-saver. Once you've written your content in your primary language, add additional languages via auto-translation*).
After a short moment of talking to the services on the interwebs, you will get the new language tab back, freshly translated from DeepL.
Now you can touch up your content and hit publish once you're ready.
*) Requires premium-feature auto-translation to be activated