In Millumin, you can copy the mapping of the selected layer using "Edit->Copy mapping only" and paste it to another layer in your second composition.
You can also Copy the whole layerstack from a composition to another (cmd+a, cmd+c in the original composition and cmd+v in a new composition)
If you have "copy layers" (as in the slice editor) you will have to relink them to the original layer by selecting the "target layer" in the right panel.
Comments
In Millumin, you can copy the mapping of the selected layer using "Edit->Copy mapping only" and paste it to another layer in your second composition.
You can also Copy the whole layerstack from a composition to another (cmd+a, cmd+c in the original composition and cmd+v in a new composition)
If you have "copy layers" (as in the slice editor) you will have to relink them to the original layer by selecting the "target layer" in the right panel.
Regards
Antoine M*