Which object would you extend to modify properties related to the text editor behavior?

The correct choice is to extend the EditorConfigProvider. This object is specifically designed to manage and configure the settings and behavior related to the text editor in Sitefinity. By extending the EditorConfigProvider, developers can customize properties such as the toolbar options, editor features, and overall functionality tailored to their specific needs. This approach allows for fine-tuning of the text editing experience offered by Sitefinity, making it well-suited for situations requiring specific text editing behaviors.

In contrast, the other options serve different purposes. The ContentsProvider is typically used for managing and providing access to content items within the Sitefinity ecosystem. The TextEditorManager plays a role in handling instances of the text editor but is not primarily used for configuring its behavior. The WidgetProvider is focused on providing capabilities and functionalities for widgets, not specifically for text editors. Thus, extending the EditorConfigProvider is the most appropriate action for modifying text editor properties.