Hi Kian Cha,
To achieve the desired behavior you need to modify the myHandler function that I sent you before:
var isCollapsed = !this.get_collapsed();
I am attaching our Dynamically Created Docks online demo
demonstrating a dynamic scenario with preservation of state where the docks have the expand/collapse behavior you would like to have. Hope you find it helpful.
. Concerning RadDock Prometheus documentation we are constantly working on improving it, so let us know if there is something specific that you do not find but think should be included in the help resources.
the Telerik team