tree-widget-after-toggle-functions is a variable defined in `tree-widget.el'.
Its value is
nil
This variable may be risky if used as a file-local variable.
Documentation:
Hooks run after toggling a tree-widget expansion.
Each function is passed a tree-widget. If the value of the :open
property is non-nil the tree has been expanded, else collapsed.
This hook should be local in the buffer setup to display widgets.