In the past, I have been able to lock an assignment until I have finished grading all of my students' work. How can I do that now?
I'm going to assume that by "lock" you are referring to muting an assignment which hid the score and comments from students until you unmuted it the assignment. A couple of months ago Canvas introduced a redesign of this process in the New Gradebook called Post Policies. The terms used now are Hide and Post (there's a little more to it but hopefully that will help you find what you are looking for). I've included links to a couple of guides below.
How do I hide grades for an assignment in the New Gradebook?
How do I post grades for an assignment in the New Gradebook?
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