web/web_widget_x2many_2d_matrix_example/views/x2m_demo.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

    <record id="view_x2m_demo_form" model="ir.ui.view">
        <field name="name">x2m.demo.form</field>
        <field name="model">x2m.demo</field>
        <field name="arch" type="xml">
            <form>
                <sheet>
                    <group>
                        <field name="name"/>
                        <field name="line_ids">
                            <tree>
                                <field name="name"/>
                                <field name="value"/>
                                <field name="user_id"/>
                            </tree>
                        </field>
                    </group>
                    <footer>
                        <button name="open_x2m_matrix" type="object"
                                string="Try x2m 2d matrix"
                                class="oe_stat_button" icon="fa-edit"/>
                    </footer>
                </sheet>
            </form>
        </field>
    </record>

    <record model="ir.ui.view" id="view_x2m_demo_tree">
        <field name="name">Demo - Tree</field>
        <field name="model">x2m.demo</field>
        <field name="arch" type="xml">
            <tree>
                <field name="name"/>
            </tree>
        </field>
    </record>

    <record id="action_x2m_demo" model="ir.actions.act_window">
        <field name="name">Demo</field>
        <field name="res_model">x2m.demo</field>
        <field name="view_type">form</field>
        <field name="view_mode">tree,form</field>
        <field name="view_id" ref="view_x2m_demo_tree"/>
    </record>

    <menuitem
    id="base_matrix_widget_menu"
    name="Demo x2m matrix widget"
    action="action_x2m_demo"/>

</odoo>