A common use case we see in report builder is to calculate percentage contribution of one row out of the entire column.
In Report builder we use column calculations to get this total value but it would be nice if we could use this dynamic column value in calculations. The alternative is to hard code the values in the object or through Data designer which might not a practical alternative.
We do this in Adoption explorer as Segments.
Percentage contribution of a Segments ARR-
Segment ARR/ Total ARR of all Segments