Modification of test cases by importing from a CSV

I have imported some test cases from a CSV file into Zephyr Scale. This worked very well. 

Now I would like to change these cases (e.g. add new steps, change test data, test results, ...) by using this import as well.

Is this possible?

I tried to add the key in my import.csv, but I did not find a Zephyr Scale field to map.

Thanks in advance for any hint