From the context menue,
besides the AREAL3D presets,
you can import and register
up to 10 user defined components,
which can be placed with the AREAL3D-tools.
Simply select a component and place it in the model.
It's name will be registered in a special file and is available from the context menu.
Once selected those components can be placed like internal elements.
Latest edit:
User-defined component can be exported to nodefiles.
From the context then you can reset the slots or load a new element.