These new icons found in the upper left of your center window of the builder will now zoom in or out of the page you are currently working on.
Until recently the only way to zoom the builder, was to zoom the entire browser. Now these icons allow you to edit the builder window and only the builder window.
This icon will return the builder screen to original size
This icon will zoom in the builder window
This icon will zoom out the builder window allowing you to see more of your handset