You can change a rubric after you've created and attached it to an assignment.
Here's how to do it:
Steps to Change a Rubric
Navigate to the assignment where you want to change the rubric
Open any student submission
In the left sidebar, locate and click on rubric under the "Global Settings" option
Select a different rubric from the available options
Click the "Regrade All" button to apply the new rubric to all submissions
