"Hide Column" in Grade Center only hides it from the instructor's view. Students will still see it listed.
"Show/Hide to Users" allows you to hide the column from your student's view. The instructor can see and edit the column information but students will not be able to view it. This can be helpful when adding comments during the grading process and then releasing them to all students at the same time.
"Delete Column" is available when a column does not have an assignment linked to it. When the instructor removes the assignment, then the associated grade center column will have a "delete" option and can be removed, no matter how the name was changed or if there's another assignment with the same name.
* If you're not seeing a "Delete Column" option on the contextual menu, it means that there's still an existing assignment associated with the column. Hint: Look for hidden columns, or a column with the name that was originally on the assignment.
NOTE: The one caveat there is that if, instead of deleting the assignment itself, the instructor deleted the folder where the assignment was deployed, then there's no way to delete the column.Tags: Blackboard, column, delete, grade center, hide, show