An exemplary method includes displaying a user interface that includes multiple panes, and receiving a first user input to select an existing node from a flow diagram or a flow element template. The system displays a moveable icon representing a new node for placement in the flow diagram. The new node specifies an operation corresponding to the selected existing node or the selected flow element template. Drop targets are displayed in the flow diagram according to dependencies between the data flow operation of the new node and operations of existing nodes. A second user input places the moveable icon over a first drop target. In response to ceasing to detect the second user input, the system inserts the new node into the flow diagram at the first drop target. The new node performs the specified data flow operation.