Dragging an item into another scene has never carried over schematic groups. This just seems to be a modo limitation (eg. it happens with modo nodal materials too).
If you drag the override into a workspace, you can see the YELLOW circles on connection. If you double click these, the rest of the nodes appear in the schematic
I'm not sure if this is something the plugin could correct automatically. Paul will have to look into it
EDIT: The safest way to deal with this is to save all your materials as presets. You can also save an item/mesh as a preset and it will save the overrides correctly. See steps to save a mesh preset at the bottom here: https://docs.otoy.com/ModoH/ModoPluginM ... do/FAQ.htm