Hi Manuel,
one way to do it is using a script unit accepting the two arrays.
The code of the script should be something like this:
#input String[] arrayOne, String[] arrayTwo
#output String[] mergedArray
def listOne = arrayOne as List
def listTwo = arrayTwo as List
def mergedList = (listOne << listTwo).flatten()
return ["mergedArray": mergedList.toArray()]
Let me know if you have any issue with this solution.