Task is to add new button at the top

1. _mainfest.py

1. add depends module

2. add view xml

                'depends' : ['hr', 'account'],
                'data': [
                    'views/hr_employee_views.xml'
                ],

                

2. model

1. add '_inherit'

2. add new field

                class HrEmployee(models.Model):
                     _inherit = 'hr.employee'
 
                    attachment_ids = fields.One2many('ir.attachment', 'id')
   
              

3. view

                <header position="inside">
                    <button name="action_create_invoice" type="object" class="btn btn-primary" string="Pay the Salary"/>
                </header>



              

Complete code of view

              <odoo>
                    <data>
                        <record id="custom_hr_employee_form" model="ir.ui.view">
                            <field name="name">custom.employee.form.view</field>
                            <field name="model">hr.employee</field>
                            <field name="inherit_id" ref="hr.view_employee_form"/>
                            <field name="arch" type="xml">
                                <field name="work_email" position="after">
                                    <field name="joining_date"/>
                                    <field name="salary_amount"/>
                                </field>
                                <xpath expr="//page[@name='personal_information']" position="after">
                                    <page name="employ_documents" string="Employee Documents">
                                        <group>
                                            <field name="attachment_ids"/>
                                        </group>
                                    </page>
                                </xpath>
                                <header position="inside">
                                    <button name="action_create_invoice" type="object" class="btn btn-primary" string="Pay the Salary"/>
                                </header>
                            </field>
                    </record>
                    </data>
                </odoo>

            

Add action_create_invoice() in model

            def action_create_invoice(self):

            

Complete code of model

            from odoo import models, fields, _
            from odoo.exceptions import UserError


            class HrEmployee(models.Model):
                _inherit = 'hr.employee'

                joining_date = fields.Date('Joining Date')
                attachment_ids = fields.One2many('ir.attachment', 'id')
                salary_amount = fields.Float('Salary')

                def action_create_invoice(self):