I've played a little with it to get a world switcher. If you want it, first file in the changeset file (download it the drag the file on an opened image).
Then the following code add three worlds named 2,3,4 and create a dock in each world.
|wm|
wm := WorldManager instance.
#('2' '3' '4') do: [:aString| wm createOrSwitchToWorldNamed: aString].
wm worlds keysAndValuesDo: [:aWorldName :aWorld| |dock|
dock := DockingBarMorph new
adhereToTop;
openInWorld: aWorld.
wm worlds keysAndValuesDo: [:aWorldName2 :aWorld2|
dock addMorph: (SimpleButtonMorph new
label: aWorldName2;
target: [wm createOrSwitchToWorldNamed: aWorldName2];
actionSelector: #value) ].
dock addMorph: (StringMorph contents: aWorldName).
].