A few times I have gone to upload an image the "similar files" tab has shown me that it would be a duplicate, so I do not finish the uploading process.
For example, a pixel-perfect duplicate from Pixiv that has an existing upload from Twitter, or an ugoira that has already been uploaded as an MP4.
In the case of duplicates that aren't much better than the existing upload, is it possible to delete the unposted file so that it does not appear in My Uploads > Unposted?