A modification that holds and executes a [SkeletonModificationStack2D].
This [SkeletonModification2D] holds a reference to a [SkeletonModificationStack2D], allowing you to use multiple modification stacks on a single [Skeleton2D]. [b]Note:[/b] The modifications in the held [SkeletonModificationStack2D] will only be executed if their execution mode matches the execution mode of the SkeletonModification2DStackHolder.
Returns the [SkeletonModificationStack2D] that this modification is holding.
Sets the [SkeletonModificationStack2D] that this modification is holding. This modification stack will then be executed when this modification is executed.