Hi @aryou,
Welcome to the Auth0 Community!
We don’t have a user impersonation feature, if you are trying to get tokens for existing users for which you do not know their password.
If you want to get a token for a test user, you could use the Authentication API Debugger Extension, set up the Resource Owner Password Flow (this allows you to directly exchange username/password for a token without the login widget), or use the “Try Connection” feature with dev tools to inspect the request and grab the token.