Hi,

In your custom module, you can add new menu as how we add normally. As you have to add this inside a existing module or at a particular position, what we have to do is to set the parent of the menu correctly.

Suppose if you need to add  a new menu under the Accounting -> Reporting -> Partner Reporting Menu, what you have to do is that, first of all you have to find the external id of the menu. To get its external id, go to settings -> technical -> user interface -> menu items, search and open the above menu from the list (make sure that debug mode is activated).  Then click on the debugger button, click view meta data, from here you can get external id of the menu.

External ID of the Accounting/Reporting/Partner Reports  menu is account_reports.account_reports_partners_reports_menu

Now when you add new menu, set this id as the parent for the menu.

              name="Search Appointment"
              parent="account_reports.account_reports_partners_reports_menu"
              action="action_searchfloa_appointment"
              sequence="30"/>

Thanks

Hi,

you can take a reference from the below link to ADD New menu with existing Menu Action in New Place.

Click Here

Click Here

Thanks & Regards,

Sunny Sheth

Yes, you would be able to add / modify menu items for a user group, the Odoo tutorial explains 

https://www.odoo.com/slides/slide/access-rights-1004?fullscreen=1