In this video, you will learn about the Vegetation Scatter tool. This tool allows you to easily place any number of selected vegetations randomly onto an object. This works primarily on horizontal surfaces as you will see in the video. Each of the vegetations used within the vegetation scatter have their own settings that can be freely adjusted.
https://dev.epicgames.com/community/learning/tutorials/8bBW/how-to-use-the-vegetation-scatter-twinmotion-2020