The properties panel is, in the author's opinion, one of the most valuable things about extensions in Qlik Sense and the general extensibility of the product as a whole. The property panel is the configuration interface between the JavaScript code and the self-service user or developer.
As such, it is essential to leverage and understand the property definition file.
First and foremost, it is recommended and best practice to capture the property definition in a separate file and load it via RequireJS to your main JavaScript file. This is done fairly simply by creating a new JavaScript file in the folder structure, suggested to be called properties.js:
In the MasteringQS.js file, you load the properties module by defining it in the top of the file structure:
//MasteringQS.js
define(['./properties', 'text!./template.html'],
function...