Hi Marco - as far as MoI itself goes under regular operation, every object that is click selected or selected by script is assigned the current selection order number and then that number is bumped up by one so the next one will have an increased number.

The number itself is not a script-accessible property, but on an object list there's a list.sortBySelectionOrder() method that can be called which will re-order objects in the object list to be in ascending selection order.

- Michael