Mike,
From my tests seems not possible to use the setup participant functionality.
Here is what I have done.
Context Team: the Design Engineer role is empty.
At ECN creation I select a the team template I want to use, which has 3 users in the Design Engineer role.
Which resolve in a team instance for the DE role:
In the activity, the "Set Up Participants" tab will auto-populate the 3 users in the team instance.
have used the "resourse pool" to restrict the user from the "Designe Engineer" role only.
If a user is removed by mistake, I cannot re-add it anymore,
In fact, when you add a user, the query is against the role in the Context Team and not the Team instance of that specific ECN.
I hope this makes sense