Feels like a clunky way of doing this, but got the job done😉
Solved! I'm glad the Multi-Row Tool exists now. That makes this substantially easier than what everyone else dealt with :)
I feel the UI is very similar to Designer Desktop :)
My solution:
Workflow
Expression in Multi-Row-Formula
IF [Row-1:Count] = [Count]
THEN [Row-1:Rank]
ELSE [Row-1:Rank] + 1
ENDIF
Output