[X-treme]

Czech is not supported by the CCC.
If you want to change it to another language you can do that with NCS Expert.
1. You can change the language inside the trace file and code it back
-OR-
2. You can change the language variant in the VO and VO code the CCC

But as said, neither of those options will work with Czech language.

That's not completely right, For changing main languages on ccc u need to flash the unit either with winkfp or with ista p. On CIC u can code it with ncsexpert.