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

For a customer, we have a custom object <strong>UsrCandidate</strong> 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 <strong>UsrCandidate</strong> record
• We want the submission to update the existing <strong>UsrCandidate</strong> 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!