Hi guys,
So after trying to find the hidden clock, I found the following path is the efficient one.
In the Air Bnb app go to:
1- Inbox - Open the chat with the guest awaiting review -
2- On top of the chat you will see the guest name, the text äwaiting review" and Details
3- Click on details and it will take you to the guest's reservation screen
It will show "COMPLETED", GUEST name, how many guests, how much they paid, the name of the listing and underneath that the message that you have x minutes to write a review.
So, in conclusion, the clock is shown on the screen where you would see all the reservation details for which you need to write a review.
Hope it helps