Hi @KamaHalal,
Thank you for posting your question to Q&A.
I would like to make a clarification that this one is achievable as I tested from my side already. Please double-check from your end to see if this works or not.
The reason why you could not implement or make this permission worked is because the Document library inherited permission from its parent.
- Go to your SharePoint site > click on Document to go to Document section > Click on Settings (at the top right) > Library settings > More Library settings (Make sure that you click on Settings when you are in Documents section)
- Click on Permission for this document library
- Click on "Stop inheriting permission", this will allow your customized permission you created earlier to be working.
- Now you could see that within the Documents section, you could add new items/documents, but you will not have the option to delete them.
Please try this and let me know once you have the update.
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