When adding Squash & Stretch to a layer, the easiest solution is often to add non-uniform scale to it. However, the normal layer scale always scales around the anchor point and often this is not what you want. Moving the anchor point is usually also not a good idea, since this requires to shift the entire motion path to compensate for the position shift. Also it usually conflicts with other things like rotations that require the anchor point to stay at the center. A better solution is to use the Transform effect. It allows you to scale around any point easily without changing the anchor point of the layer.