Hi @alex_voigt,
I guess the direct answer to your question is "no" this cannot be done easily in bulk. There may be a way to programmatically do it via the Canvas API, but that would likely be even more work to code (especially if you're not a coder by trade).
@Jeff_F gave a potential workaround for the issue for future courses/assignments, but I'm curious about your course/assignment setup. Canvas would only apply the missing tag automatically for online submission type assignments that do not have a submission. In many cases that is pretty straightforward and correct, but in your case it appears that it's not the behavior you'd like. Are you accepting work both online and on-paper and that's causing the missing tag to be incorrectly applied for students turning things in to you in-person? Are you excusing certain students from doing the assignment and that is where things are going wrong, smoething else? It may be better tyo try to figure out how to prevent the missing label from being automatically added when you don't want it, with Jeff's suggestion being one possibility.
Look forward to hearing back from you!
-Chris