The one that sprays a vertical column of loot across the screen, like crests and dreamsurge essence. I can move it and resize it via addons but it seems to be protected or something, as they can’t hide it or disable it.
There’s a lot of visual clutter in the UI…
EDIT: I think it’s a “window” and not a UI “Frame” and as such can’t actually be hidden? Is that right?