Hi,
Not sure I understand what you are trying to do. According to your code the outcome is supposed to Test_CurrentDate_CurrentTime and not Test_1_CurrentDate:CurrentTime
If you wish to add an incrementor you can intiialize a global variable at the beginning of the script run in the Init section and then increment it before any use.
Initialization in the Init section should be done in Evaluate JavaScript step like that
Global.incrementor = 0; // No need in var definition before using the Global object
Increment the value before use in the Actions section in Evaluate JavaScript step like that
Global.incrementor++;
(See another example in TruClient help center)
You can then concatenate the value as follows
var parameterName="Test_" Global.incrementor + "_" + currentDate + "_"+ currentTime
Regards,
Shlomi