Hello Yoganandam Gopal,

One possible issue could be with the "onchange" method. Make sure you don’t have two methods with the same name.

Also, it’s important to ensure that you have added the necessary dependencies to your "__manifest__.py".

Here’s a revised version of your code:

class CustomPreset(models.Model):

    _name = 'custom.preset'

    _inherit = ['mail.thread', 'mail.activity.mixin']

    name = fields.Many2one('custompreset.master', string='Name')

    rel_id = fields.One2many('custompreset.child', 'parent_field_id', string='Detail')

    search_dp = fields.Char(string='Search')

    @api.onchange('search_dp')

    def onchange_test_domain_field(self):

        mini_rec = self.env['custom.preset'].search([('id', '!=', self.id)]).name

        available_ids = []

        for i in mini_rec:

            available_ids.append(i.id)

        return {'domain': {'name': [('id', 'not in', available_ids)]}}

In this revised code, I’ve changed the search domain in the "onchange" method to exclude the current record’s ID. This should prevent the current record from appearing in the "Many2one" field dropdown.

Hope this helps

Regards,
Maciej Burzymowski