How can I switch to monthly reimports without losing finding history or Jira relationships?

Hello! Currently, each month I run a new scan and create a new Engagement in DefectDojo. We then import the Findings, run deduplication, and create/update the corresponding Jira tickets. Current workflow:

Scan
  ↓
New Engagement
  ↓
Import
  ↓
Deduplication
  ↓
Jira
  ↓
Repeat every month

We would like to move to a model where the existing Engagements are kept as historical records and, from now on, we use a single Engagement/Test with a Reimport each month. Desired workflow:

Scan
  ↓
Existing Engagement
  ↓
Reimport into the same Test
  ↓
Existing / New Findings
  ↓
Jira
  ↓
Repeat every month

The main question is how to make this transition without losing the existing Findings, their history, or their Jira relationships.