I solved my problem but i don't know if it's the best solution ... Anyway, if it could help, here is the modified "kendo.all.js" file.
Modified lines :
L 16322 : I added an option to the defaults (true : will work like the default library, false : will only activate the PanelBar on the main parent and no its children)
L 16687 - 16696 :
And here we are !
If you've got something better, i'd enjoying to hear it :)