Thank you for bringing this issue to our attention. Unfortunately, after careful consideration, we will not be addressing your issue at this time, as we are currently committed to resolving other higher-priority issues.
We acknowledge that the current Terrain system has a number of limitations, so we are currently investing in a large amount of discovery work to determine exactly what is needed most and how we can bring it to you at the quality level you have come to expect and address the most pervasive pain points in the most effective and efficient manner. However, we know each case is different, so please do continue to log any issues you find, and provide general feedback on our roadmap page to help us prioritize.
Forum to discuss feature requests: https://forum.unity.com/threads/world-building-public-roadmap-and-feature-requests.1437163/
Roadmap: https://unity.com/roadmap/unity-platform/3d-world-building