Hello Cybrosys,

Do you have some screenshots for me because I am looking in dutch version and the translates or most of the time not so good I'm afraid? Do you mean the settings underneath Odoo itselves or underneath Time off module? When I'm Superuser or normal user? Thx a lot

Hi,

You can achieve this using automated action.
First you need to create a template to send to the manager under Settings -> Email -> Email Templates.
Then create an automated action from Settings -> Automations -> Automated ActionsIn the action, 
Give name, choose model Time Off, Choose trigger as On Creation, Give Action to do as 'sent mail' and choose the email template created earlier. 

Hope it helps