I'm looking to have an anchoring something like the following image:

Where the blue box is a child of the red box (both control nodes). Preferably, they would both be able to be arbitrary sizes (and change size arbitrary) and still be stacked, the blue just above the red. Additionally, the blue will disappear and reappear without the red changing its appearance, so putting them both into another container is not ideal (unless I'm misunderstanding something about how to use that container).
Does the default anchoring system allow for this easily? Or will I need to add some code which checks the dimensions and positions them accordingly? (This would code would not be difficult, I just want to make sure I'm not missing a cleaner option if it already exists). Thank you!