To see the wave bar, open the panel configuration window by clicking on the box-like icon to the left of the search window or by going to Preferences > Layout (1) and clicking "Arrange Panels." You'll see "wavebar" in the available elements section on the right. Click on it and drag it to the desired panel on the left side of the window. It can be dragged to any panel that has a vertical bar appearing next to it when "wavebar" is cliccked.
The wavebar colors are based on the skin being used.