Hi @Anonymous
Please follow the instructions from @MarkBiggerstaf. If you are confident that you have performed every step as per the official documentation or the blogs you are following. Then the next thing you need to check is table permission.

Once you set the notes entity permission properly.
Key Note: To see the attachment option, "The record has to exist" meaning once you create the record then the attachment will only appear if you "Edit" the record. For creation/ insert mode - The attachment will not be visible.
Hope it helps.
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