Hi,

    I have a form with a field like this:

     <record model="ir.ui.view" id="point_of_sale.view_pos_config_form_test">

        <field name="name">pos.config.test</field>

        <field name="model">pos.config</field>

        <field name="priority">25</field>

        <field name="inherit_id" ref="point_of_sale.view_pos_config_form"/>

        <field name="arch" type="xml">

            <field name="journal_ids" position="after">

                <separator string="Test" colspan="4"/>

                <field name="test_ids" colspan="4" nolabel="1">

                    <tree string="Test">

                        <field name="name"/>

                    </tree>

                </field>

            </field>

        </field>

    </record>

    And this models:

    class pos_order_test(models.Model):

    _name = "pos.order.test"

    _rec_name = "name"

    name = fields.Char('Nombre')

    config_id = fields.Many2one(

        'pos.config', string='Point of Sale',

        help="The physical point of sale you will use.",

        required=True,

        index=True)

class PosConfig(models.Model):

    _inherit = 'pos.config'

    test_ids = fields.One2many('pos.order.test', 'config_id', string='Tests')

The thing is that after some Odoo upgrades "Add new item" buttom disapeared. If I force with create="true" it appears, but when you click this buttom new window inputs appear disabled.

Any clue?