You can rebuild this in Mendix. We have a webservice where tokens can be generated. Based on these tokens one can create a deeplink and with the autologin feature we log this user in (seach for autologin on the forum to find the blogpost on how to do this part). You then create a login as user button that calls the webservice for a valid login token, creates the deeplink URL and do a redirect on that URL. And voila you are loged in as that user. Note however that depending on your settings if that user is already logged in you force him with a logout because only one session for that user can exist.
You could add the User rights to your (admin) account, or just create a new account that only has the User rights and use that to see/test the user functionality.
Does that answer your question? Or what are you trying to achieve
If you are trying to log in as a specific other user and see the same things that he sees, this is not possible. If it were it would be a serious security risk.