It's been a while since I needed to change these settings so maybe I'm missing something obvious.
When I try to customize the import or export settings, specifically changing what columns will be in the CSV file, I can't remove or add any of the columns listed. Has anyone run into this issue lately?
you have some script error that causes UI to break. This may be caused by other plugins that inject scripts outside of their scope.
You can turn to support over email so they take a look and possibly discover source of problem.