How can I manually create a column in the Canvas gradebook so I can manually post a grade in that column?
You asked about creating a column and manually posting grades. Those are two things. You first must create the column, then you can tell it to manually post grades.
Columns in the gradebook that hold grades are created when you create an assignment. Go to the Assignments page, create an assignment, and as long as it is graded, it shows up in the gradebook. If you want to enter a grade, but not have students submit anything, then you can set the type of the assignment to "No Submission." Note that these will be visible to students.
Once the assignment is created, you can set it so that the grades are not automatically available to the students until you take action and post the grades. See this lesson in the Canvas Instructor Guide for more informaiton: How do I select a grade posting policy for an assignment in the Gradebook?
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