I believe the Waveform Monitor and the Vectorscope are 2 different things. The WFM button activates the Waveform Monitor but how do you activate the vectorscope? It don't seem to find it on the menus either!
The first push of the button superimposes a live waveform display on the LCD of the camera, while the electronic viewfinder remains clear so the waveform can be used constantly while using the viewfinder for composition and focusing. The second push of the button replaces the waveform with a superimposed vectorscope on the LCD. The third button push in the sequence clears the screen
Correct, assuming that you've set the SW MODE setting to show WAVE/VECT. If your SW MODE menu item for the WFM button is set to just "WAVE", then the WFM button becomes an on/off toggle for the waveform monitor. If it's set to just "VECTOR" then it becomes an on/off toggle for the vectorscope. If it's set to WAVE/VECT then it behaves as David S. described.