Is it possible to manage multiple ImageryLayerCollection like a layer group ?

[Théo]

Hi all, i am trying to have multiple collection of layers inside the base ImageryLayerCollection ( viewer.imageryLayers ) to manage lot of imagery, 

something like CustomDataSource does with the entities property

i am able to add an new ImageryLayerCollection to viewer.imageryLayers as a layer with is layers but they dont apear on the map 

is this even possible ?