So, I've created a 256x256 cells large world space with two huge lakes in it and when I tried to figure out how to flood them, I came across one of those infamous "non-features" of the CK, to wit the apparent impossibility to select multiple cells and change their parameters at once instead of going through the tedious task of doing it one by one.

Now the question is if there is an external tool with which it is possible to edit cell data in a simple way.