So here is the one I did using the Construct URL columnā¦
Started off with a URL that looked like:
https://quickchart.io/chart?bkg=white&c={.........}
There are two query parameters in that URL:
bkg=whitec={ JSON structure }
So I took the whole JSON structure, and put that in a template column:
Then defined the Construct URL column as follows:
The first query parameter was simple, so I āhard-codedā that, and the second query parameter came from the template column.
And thatās it 
Resultant chart isnāt particularly impressiveā¦

But itās what the customer wanted 

