Copy-Paste Trees in Terrain Tool?

I am using Unity terrain tool and want to make symmetrical maps, but I do not know if there is a way to select trees to copy and paste them. I want to create symmetrical maps, so I think need copy-paste tools in Unity Terrain Tool. Anybody knows about this?

There is no copy paste Terrain trees. You can get at the terraindata / tree data structures and manually work it.