The QuickFX tool is different from all of the other QuickTools. The QuickFX is intended to apply an effect to already-running cues.
The main features of the QuickFX tool are shown and described in the picture below.
As shown, you simply clock on a desired effect, and it will be applied on top of all playing cues (if the Master button is pressed) or it will be applied to only the selected cue (if the Cue button is pressed).
There are multiple Layers of FX available. This allows you to pick an effect from Layer 1, and a separate effect from Layer 2, and have both effects active simultaneously. Since there are four layers of effects, this allows up to four effects to be active at the same time.