Restart KDE
In KDE 4, you can do:
killall plasma-desktop #to stop it
kstart plasma-desktop #to restart it
In KDE 5 use:
killall plasmashell #to stop it
kstart plasmashell #to restart it
In KDE > 5.10 use:
kquitapp5 plasmashell
kstart5 plasmashell
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