This may or may not help but, this is one thing I have done.
Instead of anchoring UI items to my window, I place all UI items on a single layer. I then set the layer paralax to 0,0. This makes it so the layer does not move at all when scrolling. When the layer loads, I set the starting position of elements I want to move, relative to the layer size. I have attached a very simple example capx to show you how it works. If you press esc, a text object will drop down from above the screen. Also, there is a bottom bar with a button that will make it expand and contract. The graphics look terrible because I just wanted to throw together a quick example but, you should be able to see how it works. Also, the only thing that is anchored is the box in the upper right but it really doesn't need to be.
This may not be as flexible or even as good a method as what TheDom suggested, but it is a method I have used that worked well for me.
I hope this helps you work out some new ideas on how to handle this situation and good luck with your project.