Now that UMich has an application on record, I would think (but I’m not sure) that they will always have your info on file, even if you withdraw your app and then re-submit.
Anyhow, after UMich receives all of your info (transcripts, LoRs, counselor report), they will reach out to you (and there will be a form in your Enrollment connect portal) and ask if you want them to consider your test scores…so you should answer no.
https://admissions.umich.edu/apply/first-year-applicants/requirements-deadlines/application-changes
Ask your HS GC to help you, good luck.