Under BP_MotionControllerDetach if you are using MotionControllerMap2. There are 2 example maps, MotionControllerMap and MotionControllerMap2. The “2” uses more advanced algorithm to detach things, so it uses BP_MotionControllerDetach and MotionControllerPawnDetach.
The difference between two is how they manage the “Detach” operation.(Grip+Trigger). The first map will just call UE’s DetachFromActor. The problem is that you can easily end up holding something with a hole in the middle.
Second map will rebuild attachment trees to avoid this situation. It will use MSSR’s snap sockets to find which cube is logically attached to which one then use that to make new trees without holes. The algorithm is in BP_MSSRHelpers Detach function.