This feature would help in many cases where one has the basic design... and wants to "branch" off into variants.
If one has several variant designs with the same elements... at the present time one must download and then upload just to copy the file and make a design variation.
Perhaps this is part of the billing plan, to pay for each time you upload or download something (In such a case, I hope we are paying by the pound).
Still, a simple, native "Save as..." in the cloud, would save a lot of headaches during the design phase.
I can see how this could clog the servers if guys made multipule copies of turbine engine designs... or medical scans... perhaps these aspects make such a system more viable from a business standpoint.
But in the small part world I live in... it seems strange to work without this familiar tool.