Bug 89824 [Forms] Position of Go button in Help Search view changes
If you expand and contract the Default Scope area the position of the Go button will shift (and the combo will shrink and grow). I will attach two screencaps - note the space to the right of the Go button.
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/forms/widgets/TableWrapLayout.java
/**
	 * Number of columns to use when positioning children (default is 1).
	 */
	public int numColumns = 1;
	/**
	 * Left margin variable (default is 5).
	 */
	public int leftMargin = 5;
	/**
	 * Right margin variable (default is 5).
	 */
	public int rightMargin = 5;
	/**
	 * Top margin variable (default is 5).
	 */
	public int topMargin = 5;
	/**
	 * Botom margin variable (default is 5).
	 */
	public int bottomMargin = 5;
	/**
	 * Horizontal spacing (default is 5).