On page http://yed.yworks.com/support/manual/edit_mode.html#add_remove_node_to_group_node
there is the instruction:
"To remove a node from the contents of a group node move it out of the group node while holding down the SHIFT"
This appears to not work for me, I HAVE TO resort to the Tree/Structure view.
It would be convenient if this feature starts to work.