I have tried to assign shortcuts to activities. I tried to input the shortcuts and hit ok, but Plasma didn't save the shortcuts. Finally I saved them via Global Shortcuts, but I'm unable to use them. They don't seem to have any effect. I can walk through activities with Meta+Tab, but not directly to a specific activity with a defined shortcut. Meta+Tab is useless because some activities will be shut down at random, it seems. The ordering of the activities seems to change from session to session.

It was so much easier in Plasma 4 with different desktops without activities.

Bug 342186 - Global shortcuts do not work to control activity switching: https://bugs.kde.org/show_bug.cgi?id=342186
- marked as fixed but as the comments told it is broken

Bug 362774 - KDE Activities do not have a well-defined ordering: https://bugs.kde.org/show_bug.cgi?id=362774

volkerh wrote:It was so much easier in Plasma 4 with different desktops without activities.

You can still use different desktops (without activities) as well.

I tried to restore the functionality of multiple virtual desktops using activities. But that seems impossible because I cannot assign a specific shortcut to each activity and switching by different means takes time. Going back to virtual desktops doesn't work because I cannot have different wallpapers and widgets per desktop. There have been lots of complaints about that but to no avail.

It seems my best option is to stick with Plasma 4 until other the functionality of virtual desktop has been restored or switching between activities becomes less awkward.