When the panel setting’s scale mode is set to “scale with screen size”, the effect in the viewport is completely different from that in the game
For now, the UI Builder has absolutely no knowledge of what’s set on the PanelSettings, so you won’t see any difference in its viewport no matter what values you set on the PanelSettings.
We have the link between them on our radar to be tackled at some point, but it’s not yet the case.