A method that prepares data for analysis includes displaying a user interface that includes a data a data flow pane that displays a flow diagram having a plurality of nodes, each node specifying a respective primary operation, a change list pane corresponding to a user-selected node in the data flow pane, and a data pane that displays a plurality of rows for an intermediate dataset of the user-selected node. The method also includes, in response to receiving a user input to perform a secondary operation at the user-selected node: (i) displaying, in the change list pane, an ordered list of secondary operations performed at the user-selected node, including displaying the secondary operation, and (ii) updating the data pane in accordance with the secondary operation, including updating the plurality of rows for the intermediate dataset.