How to authenticate to client accounts without their password?


How can I get an access token for my customers without their password to access their accounts? I have a ticket-based support system where customers request help for their problems and I want to sign in their accounts to check thoroughly if the problem has resolved with their consent. But I can’t figure out how to do this. I would like to spawn a session in their accounts with one click from my management dashboard. What is the flow for that?

There used to be a user impersonation feature, but it was deprecated: