Thanks for your answers @PointC @Carl !
That's true! Now this is working like a charm ! Thanks
For information, i don't use Draggable to reorder thumbs like in your demo @Carl, I'm trying to reproduce this gallery from Poignée de Main Virile: http://fubiz.studio/projects , sorry for being poorly expressed
I don't know if i'm actually using draggable in the good way or not ...
[Update] Codepen edited