Last tested: Jan 21, 2019
Running Total Down:sum(offset_list(${measure},1-row(), row()))
Running Total Up:sum(offset_list(${measure},0,count(${dimension})-row()+1))
This content is subject to limited support.
Works great unless some of your rows are nulls in which case:
sum(offset_list(${measure},0,count(coalesce(${dimension},0))-row()+1))