Hi,

Use One2Many.

* Syntax:

fields.One2many('related_model', 'related_field')

* Example 
class HRemployee(models.Model):
    _inherit = 'hr.employee'

    compaint_ids = fields.One2many("complaint", "employee", string="Complaints")

Hope it helps

Hi,

class HrEmployee(models.Model):
 _inherit = 'hr.employee'

 complaint_ids = fields.One2many('related_model', 'related_field', string="Complaints")

class Complaint(models.Model):
    _name = 'complaint'
    _description = 'Manage employee complaint'
 
    employee = fields.Many2one('hr.employee', string="Employee", required=True)

Based on the employee selected in the 'complaint' model, records created will be related to respective employee.

Thanks

Use one2many relation for hr.employee:

class HRemployee(models.Model):
    _inherit = 'hr.employee'

    compaint_ids = fields.One2many("complaint", "employee", "Complaints")