Some free terrain tools I put together using the excellent terrain tool system included in 2018.3. The hydraulic erosion tool in particular wouldn't have been feasible without the shader functionality that's now been exposed. My work could certainly be improved but the tools suit my needs and I've still got a game to make. Feel free to modify and redistribute. https://assetstore.unity.com/packages/tools/terrain/runswimfly-terrain-tools-142156
I have to admit I'm not really familiar with it. When I downloaded the terrain tool samples I could see that there was just one contributor and the last commit was 5 months ago. I thought it might be a little presumptuous to make my own contribution there. Perhaps I was mistaken.
Hmm it doesn't have to be their github, you can create a fork of their repo and put your addition into the fork repo.
ya. feel free to fork it. that was an initial collection of tools using the new API. we've been working on a few more in the meantime. aiming to make them available 19.1-ish
https://github.com/RunSwimFlyRich/TerrainToolSamples I'll retain the package on the store. It's already had a number of downloads and is a more accessible way for the non technically minded to get hold of it.