At start, the panes in the bottom does not consume the whole window width. After undocking the panes and docking them back, the compass only shows me an option to dock the panes while consuming the whole width.
I have no option to return to the original state (like in Start.png). The only way to return to that state is undock and re-dock the right pane, and then dock and re-dock the left pane.
Visual Studio has this feature (see image), and you are probably familiar with it.
I've also noticed that Syncfusion docking manager also supports it, so it is a nice addition.