A viewer shows circuit design activities, displaying a signal, its corresponding trace, and the values of the trace over time. A global zoom-in, zoom-out, and zoom-fit are provided over the value display to adjust the time interval covered within the viewer. Non-linear manipulation of the traces within the viewer enables simultaneous zoomed in display of multiple time intervals, and zoomed out display of other time intervals. The non-linear manipulations may be performed within a same display region by designating zoom groups corresponding to the selection of a designated time period of activities of the circuit. Each zoom group may be scaled independently of other timer periods to zoom in or out of activities occurring within the designated time period. A list of behaviors may also be provided. Selection of a behavior generates a separate signal list for signals associated with the behavior and corresponding traces for enhanced debugging.