Link existing record to Marketing Landing Page to update instead of create (custom object)

For a customer, we have a custom object UsrCandidate which is initially populated from an external system.
At that point, we already know the candidate’s full name and email address.

We want to send the candidate an email with a Marketing Landing Page link, where they can complete additional information (via a web form).

Our challenge is the following:

• When the candidate submits the landing page, Creatio creates a new UsrCandidate record
• We want the submission to update the existing UsrCandidate record instead, so that there is only one record per candidate

Is there a supported way to:

• Pass the existing Candidate record ID (or another identifier) into the landing page (e.g. via URL parameters), and
• Configure the landing page so that it updates the existing record instead of creating a new one?

If possible, we would prefer a Creatio-native approach (Marketing landing pages, matching logic, hidden fields, etc.), rather than post-submission merging via a business process.

Any guidance or best practices would be much appreciated.

Thanks in advance!