There should be a tooltip when using the knife or other tools that require the waveform to be visible.

So I lost SO MUCH TIME with this. The newest UI change has, for whatever reason, caused the waveform to be collapsed... and hidden. I try and use the knife or shorten the video and nothing happens. After help from tech support I was shown that the waveform was hidden.

Tech Support sent me this gif. It shows how the editor can be set so the waveform is hidden. There is nothing indicating this has happened. It seems to be tribal knowledge and should either be prominently documented (though I can't imagine what I would search for), or the UI should be fixed so it's not possible or at least takes deliberate intent to hide the waveform.