This would also be good when you've tried to post to a stream only to find that the owner/mods are no longer active. Cancel from that stream & give it to another.
This would honestly make it more convenient. I cannot tell you how many times I've accidentally posted in the wrong stream.
We either need this or a better way to post into specific streams, like typing the name of the stream you want to post in.
You should be able to cancel an image submission. For example if you submit an image to the wrong stream you can cancel the submission and put it in the correct stream rather than deleting the image or waiting for it to be taken down