This question below was asked but not answered and I am having the same problem:
In Speedgrader, is there a way to shrink the size of the rubric? In order to see my entire rubric and the place to leave qualitative remarks, I have to move the rubric screen so far to the left that it shrinks the student submission until it's nearly illegible. Ideally, I'd be able to see both the student submission and the full rubric together. As it is now, the rubric is much bigger than it needs to be for scoring/commenting. Actually, it became worse just today; I assume Canvas made an update to the rubrics, but as a result of the update the rubric scoring is much more unwieldy.
I've included a screenshot to illustrate the problem:
Any insight is much appreciated!