A user interface that allows the user to lock in a comparison state of an inspector control that provides a view on state of a data set being subjected to transformations. The inspector control visualizes a state of at least a portion of the data set (such as a column, table or database) as that data set is navigated by a navigation control. At least under some circumstances, the inspector control also visualizes a comparison state of the data set. A comparison lock control allows the comparison state of the data set to be locked at a particular comparison state regardless of the navigation control navigating the data set. Accordingly, until the comparison state is unlocked via a comparison unlock control, the inspector control visualizes a current state of the data set along with a visualization of the locked comparison state of the data set.