I've noticed that while I can substitute images for different images in coding, such as changing the down arrow to another image without having to go into engine.pak - this does not work for a region's scrollbar.

If I did want to change the way the region's scroll bar appears I'd actually have to unpack engine.pak, edit the images, and then repack it.

Is there any other way I can do this with programming, or is it a bug which can be fixed?

Thanks
-Iron

did you try adjusting Gui.image_shape_arrow_right and similar?