I remember seeing an example, but cannot find it now.
You probably want to set http://gojs.net/latest/api/symbols/TreeLayout.html#layerStyle
layerStyle controls Nodes in Layers, but I need to align Panels situated in different branches of Node visual tree, like in different cells of parent’ table panel.
There’s no way to automatically line up any arbitrary two GraphObjects in an arbitrarily deep visual tree of a Part.
Normally you would use a Table Panel to line up GraphObjects in rows and columns, but those objects all must be immediate elements of the Table Panel, or of TableRow or TableColumn Panels within the same Table Panel.