Currently when I grade using the new grade book, I have to open the tab on each student's grade to leave a comment. I recognize I could also do this in Speedgrader but not for the assignment flags. This takes a while to do for each student, especially when I have 150+ students. In Infinite Campus, where we traditionally do our grading, this tab opens the comments and flags for all students at the same time. Marking an assignment as missing or late is really quick and adding similar comments to each student's assignment is also as quick as copying and pasting. I can also auto-fill comments and then just edit the ones I need to. It's also very easy to see all the comments I've left (see attached picture).
It would be very helpful for Canvas to mimic this in the new grade book.