You can resize features vertically and horizontally in Site Builder.
To resize a feature vertically, hover over it with the mouse cursor, click the resizing control that appears at the bottom of the feature, and drag it up or down:
When done resizing, drop the control to save the change and stop resizing.
To resize a feature horizontally, hover over it to display parallel vertical lines to the right and left. Drag one of these vertical lines and drop the line when done resizing:
Similarly, you can resize a feature that is part of a section by dragging one of the vertical lines to the right or to the left. All the features that are part of the section will be resized to identical lengths: