You can select whether it does play an album or something like “Similar Artists” or “Artist Radio”, or “Track Radio”, or “Decade Radio”, or “Library Radio”.
I can see the case for “Next Release”.
The chevrons appear on mouse-over on desktop.
On touch screens you can use a regular horizontal swipe.
This feature is not new in version 4, btw.
You might want to look at [How To] Plexamp 3.0
