Just when I thought I got it, I found out that there’s a bit more to it 
If you’re interested in what I figured out, please visit the following topic at Jmespath filter in code node not working - #3 by dickhoning and Jmespath filter in code node not working - #5 by jan
The take away from this, is that you can actually see the JSON data structure in the background by feeding the data into a Code node with the following code:
return [$input.all()]
This gives (at least) me a better insight in what the structure looks like and how to manipulate it 