Hi, Keeman-Folador, mr. drs. M.J. (Martijn) It is a pleasure to be able to help you.
Based on my understanding of the issue, I tested it locally. Hope this will helps. : )
Per my test, you can go to the Versioning settings, check Yes in Require content approval for submitted items? to open approve feature.
Then check Only users who can approve items (and the author of the item) in Who should see draft items in this document library?,
In this way, for files newly created, only the site owner and the creator of the file will be able to access the file before it is approved.
Here are the steps for your reference:
1.Go to Settings > Library settings > More Library settings.
2.Go to Versioning Settings, check Yes in Require content approval for submitted items?, and check Only users who can approve items (and the author of the item) in Who should see draft items in this document library?
- Approve file in More and Approve/Reject.
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