If you want to use a looping script to create child records, use GetRepetitionNumber ( myTable::myrepeatingField ; $counter ) with the loop counter as second parameter to get the values of the individual repetitions; only create a child record if the value of the current repetition is not empty.
Bracket notation also works: myTable::myrepeatingField [ $counter ]
I've tried using the List () to get the values in one field and then the GetValue (field;x)
I am not quite sure what you are trying to accomplish. In any case, the List() function will NOT list any empty values.
Why don't you simply import the records into a new table, and select the option to split values in repeating fields into separate records?