Alternative Tab Bar for Folders in the Bottom of Display (above other tabs: Contacts, Chats, Settings) instead of top of display.
The feature removes a level from header and makes UI more simple, because folders are secondary info, dialogs are primary. That is why tabbar for folders should not be sticky on the top.
It was in Debug Menu earlier, but hadn't become a feature.
P.S. It is not about icons, it is about place of tabbar for folders