tra_backend/hr_vacation_mngmt/views/hr_vacation.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data>
        <record id="hr_vacation_form_view" model="ir.ui.view">
            <field name="name">Leave Request</field>
            <field name="model">hr.leave</field>
            <field name="inherit_id" ref="hr_holidays.hr_leave_view_form"/>
            <field name="arch" type="xml">
                <xpath expr="//header/button[@name='action_approve']" position="before">
                    <field name="flight_ticket" invisible="1"/>
                    <button type="object" icon="fa-pencil-square-o" name="view_flight_ticket"
                                string="Flight Ticket" class="oe_stat_button" attrs="{'invisible': [('flight_ticket','=', [])]}"
                                groups="hr_holidays.group_hr_holidays_manager"/>
                </xpath>
                <button name="action_draft" position="after">
                    <button string="Book Flight Ticket" name="book_ticket" type="object"
                            groups="hr_holidays.group_hr_holidays_manager" class="oe_highlight"
                            attrs="{'invisible': ['|', '|',('state','!=','validate'), ('flight_ticket','!=',[])]}"/>
                </button>
                <field name="employee_id" position="after">
                    <field name="remaining_leaves" attrs="{'invisible': [('state','in',('validate', 'refuse'))]}"
                           readonly="1" groups="hr_holidays.group_hr_holidays_user,hr_holidays.group_hr_holidays_manager"/>
                    <field name="flight_ticket" invisible="1"/>
                </field>
                <xpath expr="//sheet" position="inside">
                    <notebook attrs="{'readonly': [('state','in',('validate', 'refuse'))]}">
                        <page string="Pending Works">
                            <field name="pending_tasks" widget="one2many_list" attrs="{'readonly': [('state','in',('validate', 'validate1','refuse'))]}">
                                <tree editable="bottom">
                                    <field name="name"/>
                                    <field name="project_id"/>
                                    <field name="description"/>
                                    <field name="leave_id" invisible="1"/>
                                    <field name="dept_id" invisible="1"/>
                                </tree>
                            </field>
                        </page>
                        <page string="Overlapping Leaves" attrs="{'invisible': ['|',('state','in',('validate', 'refuse')),('overlapping_leaves','=',[])]}"
                              groups="hr_holidays.group_hr_holidays_manager,hr_holidays.group_hr_holidays_user">
                            <field name="overlapping_leaves"/>
                        </page>
                    </notebook>
                </xpath>
            </field>
        </record>
        <record id="view_pending_task" model="ir.ui.view">
            <field name="name">pending.task.form</field>
            <field name="model">pending.task</field>
            <field name="arch" type="xml">
                <form string="Pending Tasks">
                    <group>
                        <group>
                            <field name="name"/>
                            <field name="leave_id"/>
                            <field name="project_id"/>
                        </group>
                        <group>
                            <field name="dept_id"/>
                            <field name="assigned_to"/>
                            <field name="unavailable_employee" widget="many2many_tags"
                                   groups="hr_holidays.group_hr_holidays_manager,hr_holidays.group_hr_holidays_user"/>
                        </group>
                        <group colspan="4">
                            <field name="description"/>
                        </group>
                    </group>
               </form>
            </field>
        </record>
        <record id="view_hr_leave_configuration" model="ir.ui.view">
            <field name="name">Configure Leave</field>
            <field name="model">res.config.settings</field>
            <field name="inherit_id" ref="hr_leave_request_aliasing.view_hr_leave_configuration"/>
            <field name="arch" type="xml">
                <xpath expr="//div[@name='config_leave']" position="inside">
                   <div class="col-12 col-lg-6 o_setting_box" name="config_leave_reminder">
                        <div class="o_setting_left_pane">
                            <field name="leave_reminder"/>
                        </div>
                        <div class="o_setting_right_pane">
                            <label for="leave_reminder" string="Leaves Reminder"/>
                            <div class="text-muted">
                                Send leave remainder emails to holiday managers
                            </div>
                            <div class="content-group">
                                <div class="mt16" attrs="{'invisible': [('leave_reminder', '=', False)]}">
                                    <label for="reminder_day_before" string="Days Before"/>
                                    <field name="reminder_day_before"/>
                                </div>
                            </div>
                        </div>
                    </div>
                    <div class="col-xs-12 col-md-6 o_setting_box" name="config_leave_flight_ticket">
                        <div class="o_setting_right_pane">
                            <label for="default_expense_account" string="Flight Ticket"/>
                            <div class="text-muted">
                                Choose the expence account to post the flight tickets accounting entries
                            </div>
                            <div class="content-group">
                                <div class="mt16">
                                    <label for="default_expense_account" string="Expense Account"/>
                                    <field name="default_expense_account"/>
                                </div>
                            </div>
                        </div>
                    </div>
                </xpath>
            </field>
        </record>
        <record id="view_hr_holidays_filter" model="ir.ui.view">
            <field name="name">hr holidays</field>
            <field name="model">hr.leave</field>
            <field name="inherit_id" ref="hr_holidays.hr_leave_view_form_manager"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='payslip_status']" position="after">
                    <field name="flight_ticket" invisible="1"/>
                </xpath>
            </field>
        </record>
    </data>
</odoo>