It is now below the video and has no official name :'(.
Popular youtubers Charles Trippy and Alli Speed have called it the sub bar while the shaytards are saying links in my pants :D
Us one of this to be epic...
Alli: Call it the sub bar.
Shay: haha i just seen a tweet and someone called it the pants bar so i'm stealing it >:)
The new youtube side bar