This took me some time before finally running across a working sample, so I will share how to range an array (e.g. .columns) with an index (counter):
{{range $index, $element := .columns}}
index:{{ $index }}
name:{{ $element.name }}
{{ end }}
reference: https://knausb.github.io/2014/04/hugo-template-primer/
If someone can explain why I need to create a variable (e.g. $element) please do.