In the new 2.18 release we got rid of an obsolete entity that existed in TargetProcess since primeval times and caused lots of questions and confusions from our customers. We removed Actors.
That's how the workflow edit screen looked previously — each entity state was supposed to have an Actor, and Actors were supposed to be managed for this single purpose:
Roles were supposed to be managed as well in another screen. This added confusion — what is Actor, what is Role, where Actor should be applied, where Role etc. Now Roles are used for workflow setup as well, and there are no Actors anymore.
In a nutshell, Actors were waste. We're looking now to make TargetProcess less clicky, more crispy and laconic. So we said "bye" to Actors and now go only with Roles.