Hello Greg
Thank you for your answer.
But:
I can expand and collapse the nodes with left click OK!

When doing a first right click on a node the node is still expanded and the popupmenu is shown
The second right click on the same node is ok ! no collapsing, just showing my popup.
After collapsing the node with left click, the next right click on the same node is ok ! no expanding, just popup

What is the problem with the first right click on a node ???
Best Regards
Albert