Currently, when exporting users, there is no option to identify what users are "System".
If we add to export members of "System-administrators" it won't show add-ons' users because they are "system" but they are not added to "System-administrators.
With that said, it's not possible to filter the users when we export the CSV file.
It would be great if you add a new column, for example, System and the information Yes/No.