This extension implements tree panel with checkboxes that allow selection of individual branches or leafs.
The checked nodes define a "value" of the tree that is returned as list of values separated by a configurable separator.
The first panel of this example allows editing of the tree used by other panels. It is not CheckTreePanel in fact, but RemoteTreePanel.
Other panels show CheckTreePanel in various configurations, not showing all possible though.
You can get or set "value" of the trees in text fields below them; watch the text field tooltips.
This version is feature complete and pretty well tested. Bug reports are welcome though.