suite/project_task_line/views/project_views.xml

<?xml version="1.0" encoding="UTF-8" ?>
<odoo>
    <record id="view_task_form2_inherit" model="ir.ui.view">
        <field name="name">project.task.form.inherit</field>
        <field name="model">project.task</field>
        <field name="inherit_id" ref="project.view_task_form2" />
        <field name="arch" type="xml">
            <xpath expr="//button[@name='%(project.project_task_action_sub_task)d']" position="attributes">
                <attribute name="context">{'default_name': name + ':', 'default_user_ids': user_ids, 'default_project_id': project_id, 'default_milestone_id': milestone_id, 'subtask_action': True}</attribute>
            </xpath>
            <xpath expr="//page[@name='description_page']" position="after">
                <page name="task_lines" string="Todo List">
                    <field name="line_ids" context="{'default_task_id': active_id}">
                        <tree editable="bottom">
                            <field name="sequence" widget="handle"/>
                            <field name="name"/>
                            <field name="state" widget="selection"/>
                            <field name="user_id" widget="many2one_avatar_user" domain="[('share', '=', False), ('active', '=', True)]"/>
                        </tree>
                    </field>
                </page>
            </xpath>
        </field>
    </record>
</odoo>