Polybrush is a fantastic tool for Unity, which you can use for level design, scattering prefabs, painting and sculpting meshes! In Unity 2019.2, Polybrush was added to the Package Manager, and introduced the Prefab Scatter mode!
Learn more about Polybrush here: https://ole.unity.com/polybrush
Assets used in this video:
Time Of Day (Sky): https://ole.unity.com/TimeOfDaySky
Low Poly Rocks and Plants: https://ole.unity.com/RocksAndPlants
Terrain Textures Pack Free: https://ole.unity.com/TerrainTexturesFree
Polybrush enables you to blend textures and colors, sculpt meshes, and scatter objects directly in the Unity Editor.
Combined with ProBuilder, Polybrush gives you a complete in-editor level design solution. You can also take advantage of Unity’s seamless round-tripping with digital content-creation tools (like Maya) so you can further polish models with your favorite tools.