The existing drill down functionality that is available in charts / visuals has to be predefined. I would like the ability to allow users to choose their own drill down path using cross drill / quick explore / dice capabilities that we have in other tools such as Excel. If you right click on an item in a table or chart you are provided with a list of the tables to choose from and then you can select attributes within those tables to drill down / across. Restricting users to a predefined or custom drill down is too limiting. The feature was added in Excel 2013 and is also supported in Excel Services as well - https://support.office.com/en-us/article/Drill-into-PivotTable-data-c1b11240-fc8f-4fdd-a697-629bf6f7ee0b. This feature is also available in other tools like ProClarity, PerformancePoint, Pyramid Analytics (BI Office). Enable the users to perform their own analysis based on the model (data set) relationships.