Except for enabling you to log in to the customer's account Magento 2 Login As Customer extension allows you to view the history of the customer account entrance. In the Login as Customer Log, you can see the information about the admin user, customer account and the time it was entered by the admin. 

In order to view Login as Customer Entrance Log follow these steps:

1. Navigate to Log Grid

Go to M2 Admin Panel > Customers > Login As Customer Log

2. Check entrance history.