Here's a link to my initial post which helped get me this far.
RECAP: I use a combination of a Successor formula & Join/Collect in an attempt to report for my team the next tasks and assignee(s) in our waterfall workflow. I am able to successfully return the next assignee only when there is a single successor. I need to identify instances where a task has multiple successor assignees, this can be simple text field (doesn't need to be a contact field).
Here are the 3 formulas that nearly fulfill my use case:
=JOIN(COLLECT([Assigned To]:[Assigned To], Row:Row, HAS(Suc@row, @cell)), CHAR(15) + " + ")
=SUBSTITUTE(Successor@row, ", ", CHAR(10))
=JOIN(SUCCESSORS([Task Name]@row), ",")