Hi,

Odoo uses the External ID (also known as XML ID) to identify and update existing records. If you leave this field blank or avoid it entirely, Odoo will not link the data to any existing record, and It will create a new record every time.

Even with no External ID, Odoo may still raise an error if the model has Unique constraints on fields like email, phone, and name (depending on the model). You’ll need to remove those constraints (inheriting and overriding the model) or ensure unique values.

Hope it helps.