many thanks, for teaching this lesson on basics. 

Correct.
That's what $query() was designed for. Roughly 55+ years ago. (with a different name)
https://docs.intersystems.com/iris20221/csp/docbook/Doc.View.cls?KEY=RCOS_fquery 

You just miss setting node to the found value and the indirection for the node reference
Set node = $Query(^TestGlobal("NotConfigured"))
   WRITE !,node
  FOR   {
    SET queryary=$QUERY(@node)
        QUIT:queryary=""  
        WRITE !,queryary
       SET node=queryary
  }
to avoid issues with variable scoping use %node instead of node  for proper work of indirection

Does  NewHeaderId allow NULL or is it required ?
in addition, you could try '' instead of NULL

I joined with an article and a video.
Might be an inspiration for other writers.

CloudStudio is now also available with Docker Support and on Online Demo Server 

Docker support

Prerequisites

Make sure you have git and Docker desktop installed.

Installation

Clone/git pull the repo into any local directory

git https://github.com/rcemper/Dataset-OEX-reviews.git

Run the IRIS container with your project:

docker-compose up -d --build

How to Test it

http://localhost:42773/cloudstudio/CloudStudio.Index.cls

or use Online Demo 

Thanks for asking!

Just my review from OEX:

Thanks for info1

to use ECP you need a MultiServer License. Entree (the smallest, cheapest) is note suited for it.

Table creation is excellent !
Just used it,  works perfect.

Thanks for the feedback. 
I'm fine, thanks for asking!

thanks for the confirmation.

Do you still expect some echo?
Or is the question meanwhile just out of date?