Allow me to see where library variables are used.
When working with a number of library variables, sometimes we don't name them as well as we should. Inevitably, we look at a variable and say "where is this used again? Client side transforms? A step template?" -- If Octopus was able to report which variables were used where, it could help us better remove unused variables, and help us better organize the existing ones.
Sean Killeen commented
While I say "library variables" here, it really makes sense for any variable associated with a project.