Hey Emilio! 

It's me, Emilio, from the Odooverse V17.4! 

First of all congratulations! 

I have good news for you, it is possible. In version 17.4 when you are configuring the time Off Types under the Allocation Requests section in the field "Approval" you will see multiple options.

• No validation
• By Time Off Officer 
• By Employee's Approver 
• By Employee's Approver and Time Off Officer

This will allow you to decide who could approve/reject the request. In your case, you should select the option "By Employee's Approver" so this user will be notified once a request has been raised. 

Remember that the Time Off Approver should be set under the employees form in the approvers section:

I hope you find this useful! 

Best of luck!