Which method is used to create a hierarchy in Power BI?

Creating a hierarchy in Power BI is accomplished by dragging fields into a hierarchy in the "Fields" pane. This method allows users to organize dimensions in a meaningful and structured way, facilitating better insights and analysis in reports. Hierarchies are particularly useful for drilling down into data, such as going from year to month to day, which enhances the user experience while navigating through different levels of detail.

When users drag fields into a hierarchy in the "Fields" pane, Power BI visually represents those fields as part of a hierarchical structure. This makes it easier to set up visualizations that allow for quick exploration of data at different levels, ultimately improving the efficiency and effectiveness of data analysis.

The other methods mentioned, such as using Power Query for data loading, defining relationships through the model view, and programming in DAX, have important roles in data preparation, modeling, and calculations, respectively. However, they do not reflect the direct action needed to create a hierarchy specifically within the "Fields" pane. The functionality for hierarchy creation is focused on how users can structure their data visually for analysis, making the correct answer clear and relevant to the task at hand.