The aim of most of the graph layout classes, including the 'layered' one, is to minimize the distance between nodes. Using a fixed sort order of nodes in a layer would prevent the layout routines achieve their goal so there isn't any intrinsic support for that.

You could run post-processing code on the graph after the layout completes and swap nodes on the same layer so they are sorted. I.e. for all nodes having the same Y position, swap their X positions. But that could make the links between layers longer and make them cross each other.

You could explicitly set the order of items in TreeLayouts by setting the order of Arrow objects in the box' OutgoingArrows collections. The TreeLayout follows the order of the outgoing links, so it will arrange the branches coming out from a node in that same order.