Click the control or press U to activate.
The Up / Down control, part of the Edit Color Effects control group, allows you to do a fine vertical adjustment of the position of the effects you are editing. The changes will be shown in real time in the Preview Viewport.
Move the control to the right (toward the down arrow) to move the effects downward. Move the control to the left (toward the up arrow) to adjust the position in the opposite direction.
The Up / Down control is intended to allow fine adjustment of the effects vertical position. If you wish to move the effects farther than the control will allow, you can simply drag the set of effects in the Preview Viewport as explained in the Edit Effects Tool page of this manual.
Note that this control affects all of the effects under edit simultaneously - Primary Spikes, Secondary Spikes, Soft Flare, and Ring Flare.