What is the best way to extend a built-in widget's template?

The best way to extend a built-in widget's template is to copy the widget template to your resource package and modify it. This approach allows you to customize the appearance and functionality of the widget without altering the original code, ensuring that future updates to the Sitefinity platform do not overwrite your changes. By copying the template, you create a version that can be tailored to meet your specific requirements while maintaining the integrity of the built-in functionality.

This method also encourages better practices in code management and helps avoid potential issues that could arise from directly modifying core files, which can lead to a complicated updating process and challenges in maintaining the site in the long run. Changes can be done seamlessly, and you have the flexibility to revert to the original or make adjustments as needed without risk to the base system. Customizing via your resource package centralizes your modifications, making them easier to track and manage as part of your project.