After uploads the photos get an upload status mark in the corner. Please allow it to be used for sort and show/hide options (like show all/tagged/untagged/selected).
I would like to be able to show only those that have been uploaded or to hide them to work with the rest, and the sort ability could help to see the files in a group which were sent, which had errors and which werent sent.
I understand these marks are temporal to the files as not being stored after I close the contact sheet but PM still uses them with the contact sheet so it might be used for operations like I mentioned above. And I would find them very useful.