How can I have the UI scale to the camera viewport rect instead of the screen width and height?

Unity Engine
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1

All of the panel settings seem to apply to screen dimensions. I also tried manually setting the panel.visualtree’s style.width/height/left/top values manually, but this also didn’t have the desired effect.

2

Setting the visualTree’s values didn’t work, but I was able to set the rootVisualElement’s values successfully.