Doing it manually (picking the elements to filter by index) isn’t very effective. You’d have to modify your graph every time the lsit changes.
I’d suggest using Element.GetParameterValueByName instead of Parameter.ParameterByName. ParameterByName returns the parameter element whereas GetParameterValueByName will return just the value. You can then use a conditional statement or String.Replace node to replace all ‘E’ values with ‘N’.
This will work for any list of values in any order.