Is there a way to save or printf optimize function parameters of each WFO cycle into one list/file for example by using file_append ? It would be easier to analyse parameters for variability in one list, instead of opening each .par file when running a lot of WFO cycles.

I agree. Maybe showing this in the parameters HTML page would be a good solution.

You could write a small script that reads all separate .par files and puts them together in a single file with file_append.