How to show dynamically show retake forms

Hello,
I do have a specific use-case which we cannot seem to implement.
The idea is to show a Qualtrics survey in our MOOC platform, via iFrame, where the user can fill out a regular form; and afterwards the same user will be able to come back to this form while seeing his/her earlier answers (with the possibility to change them if necessary).
In reality a new, empty form is always shown, but as stated this is not what we want to achieve here.
I know that is possible to pass a unique, anonymized, user id to the Qualtrics survey (via URL parameter) and to save this as an embedded data field.
But we don't see how we can automatically show the retake form of an already filled in form (already filled in = the same user id has been passed to Qualtrics before and the user submitted the survey).
I'm also aware of the functionality survey retake link, but this function only seems to allow moderators to sent a retake link to the respondents (action from moderator is necessary).
Again, this is unfortunately not what we are looking for, we need to find a way to automatically show a new form (if the specific user id hasn't been passed to Qualtrics survey before) OR to show the already filled in form (retake survey).
Looking forward to your insights!
Best regards,
Koen - KU Leuven