Hi @Sujata Bhuyan, i tried the code you shared but i am getting this error ValueError: dictionary update sequence element #0 has length 3; 2 is required

Hi @jo, Can you share your code here. So that I can help.

python side

# -*- coding: utf-8 -*-

from odoo import models, fields, api

class FieldsCustomDropDown(models.Model):
_inherit = 'sale.order'

selection = fields.Selection([('1', '1'), ('2', '2'), ('3', '3')])
slection_for_opt_1 = fields.Selection([('5', '6', '7')])
slection_for_opt_2 = fields.Selection([('8', '9', '10')])
slection_for_opt_3 = fields.Selection([('11', '12', '13')])
xml side

<record id="new_test_add_custom_purchase_fields_parameters_inherit" model="ir.ui.view">
<field name="name">purchase.test.add..new.custom.fields.inherited</field>
<field name="model">purchase.order</field>
<field name="inherit_id" ref="purchase.purchase_order_form"/>
<field name="arch" type="xml">
<xpath expr="//field[@name='category']"
position="after">
<field name="item"/>
</xpath>
</field>
</record>
actual selection will be around 10 options this for testing purpose i did but its not working