[Joel]

You can move objects forward and backward in the Contents popover (which is right next to the Undo button).

Bring up the popover, tap on the object list button (third from the left), tap Edit, and then you can drag objects in the list much as you can in the Layer List sidebar on the desktop version.

We'll be adding "Bring Forward" and "Send Backward" to the contextual menu in the next release.