I heard you can use LUA Scripts ?
Or the default option: Import/Export All Object Data
First, you need to Export All Object Data to some destination in your computer.
The file-type is .w3o.
After you have exported it, open your 2nd map and Import All Object Data from that data you have exported earlier.
But by using that, you will overwrite all your custom-data inside your map, and be replaced with the copied ones, starting from X000 Raw ID.