Due to the grouping and sorting, at the moment musicbee doesn't have the typical behaviour whereby if you drag something to the edge of the main panel it scrolls up or down. This would have to be implemented for your request to be useful, otherwise you could only drag tracks within the current viewable screen area.
> Currently it is necessary to drag tracks onto the album name in Library Explorer to assign them to an album.
Just to clarify, the normal way of doing this would be to highlight the target tracks and simply edit the album tag.