Hi Scott,
You can add it into the program by smart campaign or list upload with the member status as sent. Better yet, why not just use another member status to indicate they will not be sent this email in that Engagement Engine?
Here is our set up:
Nurture Email 1
Nurture Email 2
Nurture Email 3
Nurture Email 4
If we don't want them to get email 3 because they responded to a similar offer already, we would use a smart campaign to auto load anyone that was a part of those similar to email 3 as the member status exclusion.
That way, when this lead gets email 2 this week, they will skip 3 and get 4 the next week.