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>