If you have some old code that moves a frame, the only thing you should need to change is the name of the frame it moves. None of the API functions/methods related to moving/dragging frames has changed since its inception about a decade ago, but the names of some default UI frames have been changed.
You can use the "/fstack" command in-game to find the names of frames, and
browse the default UI source code if you need help figuring out the hierarchy of children and regions.