Hello Dnyaneshwar,
You can check if there are no duplicate entries in domain model by setting ‘find by Key’ option and set the key to unique ID of the entity.
Please find the link below:
https://gettingstarted.mendixcloud.com/link/module/313/lecture/2370/4.2.3-Find-by-Key
Please mark answer accepted if you find the answer useful.
Create an unique ID for that object before you import. Then you can have an import routine that first retrieves that object by that ID and refresh it or if not found create the object.
Regards,
Ronald