Although I completely understand the reasons for this new design, I don't like to have different layers with the same name. I'd love an option to forbid this, with a msg box like Rhino 4 :
"A layer with the name you specified already exists. Specify a different layer name."
I think it would be useful when there are many layers and users. I already wasted some time merging layers and repairing the tree.
Thanks for all your efforts team Rhino!
I think this has the details you need:
No I'm aware of this but I'm not talking about importing files but about users working alternatively on the same file. Or myself adding the same layer twice because I need sleep :)
Just a switch in document options to use old behavior, it shouldn't be too difficult to do...