I know that you can Ctrl+Click on a node in the tree to recursively expand the contents.
Currently, OutSystems supports Num + and Num - to expand and collapse the nodes, which is just the same as the tree view in the Windows Common Controls library, but it's missing the Num * for recursive expansion.
You can see the Num +/Num -/Num * standard behaviour in Windows Explorer, for reference.
(I know it's nitpicky, I know :) )
-- Ritchie Annand