Scale is one of the effect setting controls. For example, for Color Pairs - there are parameter scales of Smooth and Dropfall.
You can change the parameter value by moving a slider on the scale. For this purpose, put the cursor to the slide on the scale, push the left button, and, holding it pressed, move the slider to the right/to the left. Moving the slider to the left you will reduce the value, and moving the slider to the right you will increase it. It is also possible to move the slider by a left-click on the scale, thus the slider will be moved to this place on a scale.