I'm also interested how to implement ElasticSearch

You could probably do something like this currently, but it would likely require you to write a plugin to save the osTicket logs to a log file... or writing a script to export the logs from the database to a file. Then you could have filebeat (I think its called FileBeat) send the logs to your ELK server.

If there was something else that you wanted for a dashboard you could write a script and some queries to pull the date that you want and then repeat.