I noticed there are three(!) places in System Settings from which one can set a keyboard layout switch shortcut:
1) Shortcuts -> Global Shortcuts -> KDE Keyboard Layout Switcher
2) Shortcuts -> Global Shortcuts -> kxkb
3) Input Devices -> Keyboard -> Layouts
Now, I'm a little bit confused, which one should I use... I also noticed that 1) and 3) "Alternative Shortcut" have the same value. I like the abilities to configure KDE, but in this case I think the possibilities are too many