Thanks Rickey,
I was about to provide a similar explanation. One minor clarification. You do not need to click on the arrow icon to get the pane to undock. That was true in the initial release. Now you can just click and drag the title bar which is a more natural behavior. The icon remains as an indication that the widget can be undocked.
In addition to allowing the sidebar widget to be undocked, there is an older style floating window with `type: 'floating'`, If you click on the 'Help' link in the upper-right corner you'll see a modal non-movable version of this. I expect that the floating widget will evolve to have similar behavior to that of an undocked titlePane widget shown in Rickey's screenshot.