Which panel would you use to edit the width and height of an existing shape?

The Transform panel is the appropriate choice for editing the width and height of an existing shape because it provides direct control over various transformations. It allows users to input specific values for width and height, enabling precise adjustments to any selected object. This panel can also be used to rotate, skew, or move an object, making it a versatile tool for modifying shapes.

While the Properties panel also includes some transformation options, it primarily serves as a broader interface displaying various properties of the selected object, including appearance and attributes rather than focusing exclusively on transformation controls. The Layers panel is designed for managing the stacking order and visibility of objects but does not alter shapes' dimensions directly. The Stroke panel is dedicated to editing stroke properties, such as width and style of outlines, rather than modifying the fundamental size of the shape itself. Hence, the Transform panel stands out as the most suitable option for adjusting an object's dimensions.