"Flow Step: Would this be "Send Email"? Again, this feels kind of redundant given that the Engagement Program assumes email send."
Hi Kim,
The "not was sent email" filter is not necessary. A better option is if a lead is sent that email, make them a member of the Program in question. When you put Programs into a CEE stream, the CEE logic will check 2 things:
1. Did the lead already trigger this item in the stream?
2. Are they a member of that Program?
If EITHER is true, they will skip that content. My recommendation is when you do send them a particular email, update their Program Status to "sent email" or something to that effect. It will serve the same purpose as your "not was sent email" but I believe its cleaner and less error prone.
Let me know if you need any clarification.