synthetic image

I have a brightness effect that I made within the advanced image synthesizer. When I apply a quick fx color, it removes that effect. I can change the color within the cue and it still show the effect. How do I stop this override from quick fx?

Not sure if this is the correct terminology. What i would like to do is create a cue where shape act as a mask, only allowing other layers to be displayed inside its shape, or conversely other layers run underneath the specific shape. how is this achieved? Thanks in advance for the advise