detect on tree whether expand/collapse icon is clicked

[Madottati]

Is it possible to detect, whether user clicks on the +- Icons to expand/collapse tree items?

[OEM_Dev]

Yes, the tree control has events for both

http://zone.ni.com/reference/en-XX/help/371361H-01/lvprop/treecontrol_e/

[paul_cardinale]

With an event structure you can capture Item open & close events.

[Ben_Manthey]

You can also just use a 'Mouse Up' (or Down) event. This will generate the coordinates of where you clicked. There is an Invoke Node that then turns this into the name of the item checked. 

See my attached code that decides if a clicked item is expandable and if it isn't it changes the icon.