This does not exist in Limesurvey the way you want it.
There are two types of users:
- Survey Administrators (those that have an account in your LS backend): the generally create and administer surveys.
- Survey takers: They don't have an account for the backend. You might use tokens here.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
No support via private message.