In Export Layers, it is currently not possible for layers to inherit the layer effects of its parent group(s).

Possible ways to implement this:

• Change Apply opacity from group layers to a more generic action that allows applying layer effects (and perhaps some other attributes from the group, if applicable).
• When creating copies of images to be exported, preserve the layer hierarchy, i.e. also create parent groups along with their names, effects, and other attributes copied from their original counterparts. This would also affect other built-in actions, e.g. multi-layer images supporting layers would now have their hierarchies preserved. Also, this way, the preview in Edit Layers and Export Layers would correctly display each layer with its parent group effects applied. On the other hand, this would also cause the child layers to inherit the opacity from its parents. We should thus optionally allow not applying any parent attributes or effects.

Discussed in #86