1. In your search view, please add Group By filter

<record id="bt_overtime_management_search" model="ir.ui.view">

<field name="name">br.hr.overtime.search</field>

<field name="model">bt.hr.overtime</field>

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

<field name="employee_id"/>

<group expand="0" string="Group By">

<filter name="group_employee" string="Employee" context="{'group_by':'employee_id'}"/>

</group>

</field>

</record>

2. And Define your filter as a default filter in your search view

<record id="action_bt_overtime_management" model="ir.actions.act_window">

<field name="name">Overtime</field>

<field name="type">ir.actions.act_window</field>

<field name="res_model">bt.hr.overtime</field>

<field name="view_type">form</field>

<field name="view_mode">tree,form</field>

<field name="context">{'search_default_group_employee': 1}</field>

<field name="search_view_id" ref="bt_overtime_management_search"/>

<field name="help" type="html">

<p class="oe_view_nocontent_create">

Create Overtime Request

</p>

</field>

</record>