Control nodes ( green ) do not inherit position of 2dNodes ( blue ). This is because Node2d uses position/globalposition, while Control uses rectposition. You should manually do it like :
ChestInterfaceChild.global_rect_position = ChestInterface.global_position
If You mean, that the control children of control parent are invisible, than You surely forgot to set minimal size of children. If it is 0, it will shrink to scale 0.