This was the narrow sidebar vs the full one on osx
Sidebar.png
Now you can only disable it and get the top bar only:
Screenshot 2020-08-21 at 16.21.13.png
@krischik I also liked the wide version because the vertical arrangement of the button is strange for me.
Hope it comes back , or we can make a feature request to out the setting back, maybe they forgot it 🙂