The Release Relationship Editor needs drag & drop support. I see 2 drop zones on each track. On the left is the recording relations, and on the right are the works relations drop zone. Entities dropped on the relevant side will effect what happens next. I've thought up several use cases so far:

1. Drag an entity onto a recording: Dragging an entity onto a recording such as an artist will create an artist/recording relation, drag that artist onto a work on on the other side will prompt the creation of an artist/work relation.
2. Drag a relationship between entities will simply move it.
3. Option-drag (or the local equivalent mouse/keyboard combo) a relationship between entities will copy it.
4. Dates! Dragging a date will move it between relations, option dragging it will copy it to the target relation.
5. Recordings: Drag one recording to anther to create a recording/recording relation.
6. Works: Drag a work to another work to create a relation between the two. Drag a work to another track to move it. Option drag a work to a recording to copy the existing relation.
7. Release area: Drop an artist or place entity here to create a new relation with it. Drop on an existing relation type to create one of the same there automatically.
8. Release group area: Same as release area.

This list is incomplete as it stands, but I'm sure we can figure them all out.