Seat plans can be complex, they are hundreds of products in a category of sub categories.
In order to properly "clone" (copy exactly) we should identify every row of the data with a Section ID.
We can do that with the Section ID updater. You will find this feature identified by the [S] icon in the Admin>Products associated with the main category of the seat plan event you want to clone.
Click on the icon and agree to modify the Section ID for the event category.
With that completed, now it should be OK to start the cloning process.
On the same page click the Clone Icon (2 file folders)
You will see a detailed description about the cloning process you are about to perform including a suggestion that you should always back up before cloning.
Click the CLONE button and wait.
The system will make an exact copy of your event category.
It will usually appear AFTER the original copy and will be identified by a higher cPath ID