As documented in https://github.com/camunda/camunda-optimize/wiki/REST-API-documentation#export please pass this query parameter on calling the export endpoint in order to exclude the columns as currently excluded by the user.

AT

• "excludedColumns" query parameter is passed on calling

  GET /api/export/csv/{reportId}/{fileName}

  when there are excluded columns

note:
the name of the columns equals those in the CSV header, e.g. "processDefinitionKey" or "variable:amount"