YouTube is experimenting a new user channel layout on their opt-in page. In the new channel layout, the latest video will be showing to the left, and new editor is simple to use; lets you preview changes. Just below top bar, you'll see some extra buttons, "Settings", "Themes", "Modules". Also, in the upper-right corner, you should see a little "edit" button, to help you customize the part of the page you're looking at. Also included a player that lets you view recently uploaded videos, favorites, playlists without leaving the page. YouTube created a blog to post information about the updated channels.
Source:→ Google OS