I must have stated it wrong way. My question is not about the deRegUserTriggers() function itself but about function which is passed to it. In my case it is _defCR8I_CB which does not require any arguments itself. Initially, I created it without any parameters and tried to pass it as it is:
The commands worked OK but when tried to open any layout cellview CIW reported:
*Error* _defCR8I_CB: too many arguments (0 expected, 1 given) - ((nil wasPushed nil prependList nil ... ))
*WARNING* A Skill error occurred in function _defCR8I_CB
That's why I had to define the redundant _defCR8I_CB(opt) parameter in order to avoid the error, but I do not really understand how it works.