Incidents created by history cleanup job are not related with any process instance and therefore can not be reached from Cockpit for now.

Incidents related with history cleanup job may be requested from REST API like this:
GET /history/find-cleanup-job https://docs.camunda.org/manual/latest/reference/rest/history/get-history-cleanup-job/
GET /incident?configuration=someJobId https://docs.camunda.org/manual/latest/reference/rest/incident/get-query/

Questions to be asked before implementation:

1. Are we showing historic incidents?
2. Can it be more than one incident related with the job?
3. Where and how exactly in Cockpit they must be shown?