Despite this being marked as solved in other threads, this does not work when a record does not exist to be aggregated. It will work if there is a record to be aggregated but contains a NULL value in the field being included in the pivot, but NOT when the record does not exist.. IE pivoting a table with a date, other dimension, value. If your column is date, and your other dimension is the row, there may be some dates in the filtered range that have a record and some dates where there was no record. The Null value solution does not handle this.
Would be good if quicksight could actually support a default for empty value cells since it seems to be a request that has been raised more than once already.