ok found ... I made it thru manual queries on table CMS_tree..
But It should be very useful if :

1 when you create document templates with custom attributes , if you could specify
that the table you're using for this already exists, and you should just have to "import" structure....

2 In content pane, using this document template, having the ability to recreate tree structure
with a single click .... in case the underlying database is updated from outside the cms AND/OR you have a prefilled table with hundred of rows ...and don't want to create nodes manually...