In the release editor, we can collapse mediums and leave visible only the ones we want to work on, which helps focus. When editing something like http://musicbrainz.org/release/596bd1e0-76ed-4064-84f4-b98ffce2d55f/edit-relationships it'd be very useful to be able to do the same and hide, say, the first medium once that's ready, to avoid having to go up and down the page every time.

Edit by yvanzo: Not only that but also, loading the too many mediums only when needed/expanded will make opening the release relationship editor for big releases much more faster and reliable. It implies having collapsed mediums when there are more than 10 mediums or 100 tracks.