Hi George, and welcome to the community!
Yes, the only way to have a column in the gradebook is to tie it to an assignment. If you delete the assignment or make it a non-graded assignment, it will no longer be reflected in the gradebook. The flip side is true as well - you cannot have a graded assignment that is not reflected in Grades. In order to change the point value associated with an assignment after you have initially created it, edit the assignment and change the points possible.
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