The Comala Workflows app keeps a full audit trail of key events such as changes to configuration, templates and parameters.
Confluence 5.9.x and earlier
The audit log is accessed in Space Tools and looks like this:
Confluence 5.10.0 and later
The Comala Workflows app now uses the main Confluence Audit Log.
If you were using Comala Workflows on earlier versions of Confluence and then upgraded to Confluence 5.10+, you'll see the old audit trail beneath the message about the Confluence Audit Log.