The constructor of DefaultDockActionSource can take a “LocationHint”, and a LocationHint can tell the framework where to place the actions. Like:
DockActionSource source = new DefaultDockActionSource( hint, ... );```
If you need actions on both sides of the maximize action, then you'll have to use more than one DockActionSource with different LocationHints. For that you have to implement an ["ActionGuard"](http://dock.javaforge.com/dockingFrames_v1.0.8/doc/bibliothek/gui/dock/action/ActionGuard.html).