Hi PILOU,
>> seems there is an error when i want copy a node...

Thanks for reporting the issue.
I couldn't regenerate the error here, but if you're still getting this error, please post the .nod file, so I can take a look.
Could you tell me which method you used to copy the nodes that caused the issue?
1- Right clicking on nodes and copy
2- Pressing Ctrl key and dragging nodes
3- Using shortcut ( Ctrl+C )

>> 3 different cubes are drawn : how to integrated them as 3 different nodes selected ?

You can use the "Concat" node under "General/Concat". ( See attached node )
Right click on the node to add more input slots via"Inputs " menu.
If you need to remove a slot, right click on the last input slot and select "Remove Slot".

>> No Video like this for NodeEditor Plus ?

Unfortunately, There is not much tutorial contents for Node Editor Plus right now.
Here are a few examples. I'll update it if I find more.
https://moi3d.com/forum/messages.php?webtag=MOI&msg=11886.1
https://moi3d.com/forum/messages.php?webtag=MOI&msg=11887.1