Email notification when Position set to filled

I’m looking for a way to send an email notification to the admin of the site – when a position is set to filled. I saw this thread, which looks very useful:

https://mikejolley.com/2013/12/24/using-post-status-transitions-send-custom-alerts-wp-job-manager/

Following up to this post, what custom action can I hook into here?
Are there a list of actions/filters used in which I could refer to?

Thanks in advance

https://wordpress.org/plugins/wp-job-manager/