I think this is already implemented in the core plugin

I’ve used CFS for ages and only fairly recently noticed this in the docs. Not sure if it’s new or if I’ve just overlooked it!

https://customfieldsuite.com/field-types/loop.html

(optional) Override the “Loop Row” header text. You can also dynamically populate the row label with field values. If you have a text field named “first_name”, enter {first_name} to use the field value as the row label.