I feel like this thread is all me haha.
I’ve figured it out with this:
delay = 1.5; //number of frames to delay
d = delay*thisComp.frameDuration*(index - 1);
linear(effect("Completion")("Slider"),0,100,
effect("Point A")("Layer").transform.position.valueAtTime(time - d),
effect("Point B")("Layer").transform.position)