When working with complex rigs, you may want to group layers together to avoid cluttering the Timeline view and keep your layers organized.
Groups can also be useful if you need to apply the same effect to several layers at once. For example, if transparency is applied to each individual layer making a character rig, the seams between its body parts will become visible. Instead, if you group all of the rig's layers together, then add a Transparency effect to the group, Harmony will compose the layers inside the group into a single image before applying the effect.
