child rows - custom renderer

lumo

i am trying to use a custom renderer for child rows
but i already fail at reproducing the example from the examples page:
https://datatables.net/extensions/responsive/examples/child-rows/custom-renderer.html

i created an offline version, which fails, therefore i tried to create an fiddle - and i was able to reproduce the problem:
no custom renderer is shown at all

what am i doing wrong?
https://jsfiddle.net/Lrwbt9j8/

my next step would be adding button elements which modify (json) data on click (will async call the server and update the json-data) using the servers response) this needs to update the child-renderer to make the changes visible.

Thanks in Advance

colin

That happens automatically with Editor - see here - so it would be worth considering that,

Colin