I am afraid that currently the method is not available - we will log this as a bug and will do our best to provide a fix as soon as possible. As a small sign of our appreciation for this discovery I updated your Telerik points.
Meanwhile, as a workaround please set the link as content:
What I've done as a workaround is change the renderContent function in UI/MenuItem.php. This way you will be able to use the url function on the item.
answered on 22 Apr 2013, 08:41 AM
Thank you for the feedback.
I am glad to inform you that this bug is fixed in the latest internal build. Please download it and give it a try. The syntax for creating the menu item is: