Hello Shwa and Kdagsjm, As Kdagsjm says you can use the Unity terrain brushes on the heightmap and also if you would generate again it will be reset to default. However for the heightmap you can also export the new heightmaps and then import them again so you keep the manually changes (in TerrainComposer). With heightmap output button and export output button activated you can export. As for trees if you change them manually and regenerate them again you will loose the manual placed trees. I'm making a new update where you can export and import trees/grass. So any manual changes are saved. I'm finished with the trees and only have to do the grass, now I'm busy with moving house but at the end of this week the new update will be there. So you can save and import tree maps (multiple on top of each other) globaly. And then set the density, scale and tree type of each tree in the imported tree maps.