I know it’s not currently possible to duplicate a CMS collection (data structure). I imagine that one of the challenges is dealing with whether to copy the existing data over.
I think the straightforward method would be for all of your existing Collections to show up as templates under the New collection screen. Then you can just select from your existing collections to pre-fill the new one and adjust as needed.
For data, the user could export the data from their old collection, edit it in Excel if desired, then upload it to the new one. This part of the functionality already exists.