Template variables are for DEV users as it requires a deeper understanding of the internal data model. However, if you know what pre-existing “Template Variables” to use, then you can simply select it in the list.

Template Variable

Select or create a template variable. The template variable can access to any of the internal data Model of Boxalino to calculate a specific value.

Mustache Template (Advanced)

In the advanced view you can directly typed a Mustache template: https://mustache.github.io/