I am able to create an action of type "Invoke Custom Automation" in 5.4.5.0 and I have verified that it works properly by attaching it to a Policy profile and letting it run InspectMe on Tag Complete.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2016-0171.html