in the upper right panel, you can high light all the objects in a map you want to duplicate else where, just copy them.
they will be replicated in the new map exactly in the same spot u copied them, so I suggest moving them to the “ideal” place before copying them, you can do this afterwards too I guess, ur call. also once u have copied them over for the first time, they will all be highlighted, so its easy to move them all around if you want.
and then open the map you want to copy them in, click over in the upper right panel again and paste.
both maps must be in the same content folder for this to work, so u must migrate first if they are not, but u aready know how to migrate, so ur only seconds away from merging the maps.
hope this helps.
God Bless you. May Jesus Christ be Charitable unto you.
John 3 : 16, google it, its Awesome.