The waveform scope in invideo Editor shows the distribution of image brightness. Use it alongside the Monitor to understand how shadows, mid-tones and highlights change as you adjust the shot.
Compare similar shots for sudden differences in brightness, then check whether those differences fit the scene. Keep watching the picture as well as the scope: a deliberately dark scene does not need to resemble a bright exterior. A scope helps you judge the signal; it does not choose the creative look for you.