I just tried this as well on a shape layer. In this instance, I have a shape layer with various groups which I want to fade in one after another. I amended the expression to the one below and applied it to all shape layer groups except the first one (which has got the opacity keyframes). Unfortunately they all fade in at the same time after the delay.
Also, is there a way to randomize the sequence (think “lights of a city skyline switch on”)
Cheers.
Dan
thisComp.layer("Lights Back Outlines").content("Group 1").transform.opacity.valueAtTime(time-0.5)