Day 29 - My solution not storing collection variable "newPayload"

I have followed the Day-29 challenge. I end up with the “echo webhook” monitor and can see it passing successfully with the appropriate monitor console output.

The only doubt I have is that I don’t seem to end up with a collection variable called “newPayload”. I’d expect it as a result of the below pre-request script for the “POST echo” request.

The collection variable should be plain to see when i go to the variables tab of the collection. Am I wrong in my expectation?

Many thanks