If you turn off the lights in the room, you may see the entire waveform glowing faintly.
In the analog scope days, we used storage scopes to view slow or single-sweep waveforms. A storage scope has a cleverly designed CRT with adjustable persistence. Simply crank up the persistence knob, and the waveform remains glowing on the screen for as long as you wish. That was very helpful for the slow sweep rates in sampling scopes, TDRs, and spectrum analyzers. I still use a many-GHz sampling TDR in an old Tektronix storage scope mainframe.
Today, digital scopes store the waveform in memory, and display it in various convenient ways.