Rectangle
You can create a Rectangle by dropping the Rectangle block, from the Blocks view, on the scene.

You can change the size of the Rectangle in the Size section or you can use the Size tool.

Since Phaser 4, you can set the Rounded property to give rounded corners to the rectangle. By default it is set to 0 (no rounded corners).

The Rectangle code is generated by the scene compiler using the rectangle object factory:
const rectangle = this.add.rectangle(10, 10, 100, 100);