With headers this is working like charm and a very usefull feature. It would be also very usefull in the request body json or XML to have the same functionallity.
Could you explain your situation more specifically? It would help us grasp your requirements more clearly.
For example on the first image I see the variable value, on hover over.
And here in the body this would be also a nice feature. (second image)
Thanks for the feedback, we will think about how to optimize it.