How can I set up the "Log Event" alert action in a distributed environment?

Hello, I am trying to use the new alert action "Log event" in a distributed environment (Search Head 6.4.0 & Indexers 6.2.2). Unfortunately, I doesn't work properly. For the test, I set the "main" index as the destination index. First issue: it seems that it is writing in "main" index, but on the Search Head, not on the Indexer (there is no way to indicate onto which Search peer to write the log by the way..) Second issue: I cannot see the written log. When I search `index=main`, there is no result. I only guess that the event is written because when I go to the "Indexes" pages in the setting, the "Latest event" time is updated. Any idea how to make it work?