I don't know about everyone else, but when a report references a column that is deleted, it's not easy for me to figure out which column is missing.
Sometimes I remove the wrong one thinking it's the culprit. So I start deleting until I find the one, refresh the report to bring them all back, then remove the one that worked. Sometimes this doesn't work if the report gets saved and that's annoying.
Feature Request: Somehow make it easier to see which of the columns is missing. One idea would be to make the text for those items red. You could also put a red * asterix next to the column name in the menu.
Here's an example: I've highlighted in yellow the places I think would be great to be highlighted with Red Text or an Asterix.