flectra/addons/sale_timesheet/views/project_task_views.xml

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

    <record id="project_project_view_kanban_inherit_sale_timesheet" model="ir.ui.view">
        <field name="name">project.project.kanban.inherit.sale.timesheet</field>
        <field name="model">project.project</field>
        <field name="inherit_id" ref="hr_timesheet.view_project_kanban_inherited"/>
        <field name="arch" type="xml">
            <xpath expr="//a[@t-if='record.allow_timesheets.raw_value']" position="replace">
                <a t-if="record.allow_timesheets.raw_value" name="action_view_timesheet" type="object" class="o_project_kanban_box" groups="hr_timesheet.group_hr_timesheet_user">
                    <div>
                        <span class="o_label">Overview</span>
                    </div>
                </a>
            </xpath>
        </field>
    </record>

        <record id="view_sale_service_inherit_form2" model="ir.ui.view">
            <field name="name">sale.service.form.view.inherit</field>
            <field name="model">project.task</field>
            <field name="groups_id" eval="[(4, ref('base.group_user'))]"/>
            <field name="inherit_id" ref="project.view_task_form2"/>
            <field name="arch" type="xml">
                <xpath expr="//button[@name='toggle_active']" position="before">
                    <button type="object" name="action_view_so"
                            class="oe_stat_button" icon="fa-dollar"
                            attrs="{'invisible': [('sale_line_id', '=', False)]}"
                            string="Sales Order"/>
                </xpath>
                <field name="user_id" position="after">
                    <field name="sale_line_id" string="Sales Order Item" attrs="{'invisible': [('partner_id', '=', False)], 'readonly': [('parent_id', '!=', False)]}" options='{"no_open": True, "no_create": True}'/>
                </field>
            </field>
        </record>

        <record id="project_task_view_form_inherit_sale_timesheet" model="ir.ui.view">
            <field name="name">project.task.form.inherit.timesheet</field>
            <field name="model">project.task</field>
            <field name="inherit_id" ref="hr_timesheet.view_task_form2_inherited"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='timesheet_ids']/tree" position="attributes">
                    <attribute name="decoration-muted">timesheet_invoice_id != False</attribute>
                </xpath>
                <xpath expr="//field[@name='timesheet_ids']/tree" position="inside">
                    <field name="timesheet_invoice_id" invisible="1"/>
                </xpath>
            </field>
        </record>
</flectra>