Il vaut peut-être mieux poser les questions en français sur le forum francophone! ;) http://moi3d.com/forum/index.php?webtag=MOI_FRANCAIS

I don't believe there are yet some layers and arborescence system inside Moi3D!
Just Names, Colors but any selection can have any Names & Colors !
It's sufficient for tricky intricated selections who are not possible in classical layer modes! :)