Good news... magnetism is implemented for the next maintenance release. The ability to prevent resizing on tool windows in a floating state is also included. This allows for tool window behavior similar to Photoshop.
Our implementation will align the corners of tool windows and if none are found will try to align edges. There are two properties, one is the distance at which magnetism takes effect and the other indicates the gap that snapped tool windows will be spaced apart. This way when the snap together you can tell it to keep a small gap between them.
As for the feature request of having them move as a group, I don't think we're going to do that. That same sort of feature can be achieved by simply docking two floating tool windows together in the same container. And if you did want to keep them floating and close to each other, it's very easy now with the magnetism enabled to move one and then quickly move the other one directly under it.