Configure multiple keyboard layouts: how?

Hi all,

When I boot with 'knoppix lang=ie' I get perfect Irish environment: English, Dublin timezone, correct keyboard layout, ISO-8859-15 character set, etc. When I boot with 'knoppix lang=cs' I get perfect Czech environment: Czech, Prague timezone, complete Czech keyboard, ISO-8859-2 character set, etc. So far all good.
What I would like is to have Irish environment that also supports the Czech keyboard. I boot with 'knoppix lang=ie'. After everything comes up, I go to the KDE Keyboard Tool (right-click on the little Irish flag on the taskbar) Configuration and add the Czech (Czechia?) keyboard layout (I also chose the "qwerty variant", but that should not be important). Unfortunately, in this setup I cannot type several of the special Czech characters!
What am I missing? How do I fix it?

TIA for any help.