I am assuming you are referring to the Decoration option for smooth terrain, if so you can’t really change anything about its behavior right now unfortunately.
They most likely will add that functionality in the future though.
What @Phirsts mentioned the standard Roblox decoration does not give you the ability to change anything about it yet. If it is a dealbreaker try searching for a plugin that maybe gives more settings although it will probably be hard to find one with good quality that won’t lag your game.
Here’s a plugin that is useful for placing props and stuff like that on the ground.
You can make some tallgrass or anything else really to blend with the terrain grass, but use the decorations sparingly, you don’t wanna make the game memory too high