Hello,
very often the following happend and i think it could be usefull to have somewhere a menuentry or a button "Mark this file as downloaded".
1.I search for a file
2.I start the download
3.After finished download some parts i press "preview" and see the movie is wrong or after some time i notice the file is not complete somewhere.
4.I press "Cancel" in the context menu.
5.On day later i search for the same file again
6.Back to step 2 again, because i cant memorize the filename and the color in the search pane is "Not downloaded".

Peter

There is a work-around for that...

When you have discovered that the movie doesn't fit your needs (e.g. dubbed in other language, poor quality etc), you can add a comment for that movie in the Shared FIles page..

If you add the file for download later, you will immediately have a rating-icon in your download page, and once you click it, you can see your own (and other if present) comment..
Unfortunately, your comment/rating won't be visible when searching, because ratings are only shown for files in search page, when you actually share the file..

But still, it could be a usefull work-around...

Well you can't mark something as downloaded if you've not actually fully downloaded it. There might be situations where you do need to re-start some incomplete files again but they are marked as completed and downloaded, so it can work against you as well.

I cannot see a conflict.
Mark as downloaded can store the file in known.met. If one want to download the file again, one can remove it by using show all known files.