> And not only tabs for apps like browser and IDEs, but also the desktop window manager should support tabs on top level windows in a consistent manner

I miss the tabbed window feature in KDE 4. This is the feature I'm most disappointed to see missing from version 5.

- https://bugs.kde.org/show_bug.cgi?id=343690 - https://community.kde.org/Plasma/5.4_Errata

I think this is a really essential feature when displaying tiled windows.