Kibana snapshot and restore policies - how to set snapshot retention, meaning how long to keep specific snapshots

Hi

Elastic and kibana 7.4.2

There is this feature in kibana, that I can create snapshot policies to automatically back up my cluster.

My question is, how the old snapshots are getting deleted automatically and how can I set the retention for that..?
At the moment, there seems no way to achieve this.

Raul