This is a paid asset, but now you can download Easy Scatter : Prefab brush Free.
Detail this asset from Unity Store: Original Link
Easy Scatter v1.2.0 (Latest version)
Easy Scatter v1.1.9
Easy Scatter v1.1.4
Easy Scatter is Unity editor extension that allows to paint mesh object or prefab rather than drag and drop into your scene. You will save time and make your level design creation more intuitive and simpler.
The ideal complement to Gaia
Various alignment options, randomly Rotate, Scale, work on selection will allow to Prototype your level in minutes. Above all, make your unique scenes, in applying positioning, rotations and making random scale wherever you want
Easy Scatter works on land & meshes according to their collider, and incorporates very useful options such as: resizing particles and or light range according to the scaling setting.
No media is provided