@paul_fynn ...
Thank you for posting those links. I would just like to clarify, though, that @beth_schlenker appears to be asking about how to have multiple people grading assignments in Canvas courses, yet she wants to keep their names anonymous. The first link you provided does not cover that topic. The second link partially addresses the topic...but only with annotations in the SpeedGrader. The first two paragraphs in the light blue box at the top of the second link you provided state the following ( (blue highlighting is my own):
When creating an assignment, you can enable anonymous instructor annotations in DocViewer supported submissions. When students view a submission with anonymous instructor annotations in DocViewer, comments do not display an instructor's name.
This option only affects comments added in DocViewer in the SpeedGrader submission window. Comments added in the Speedgrader sidebar are not anonymous.
Hopefully this will help to clarify how things currently work within SpeedGrader.
Please let Community members know if you have any other questions about this...thanks!