+1, this is a crucial feature for my game too.
Like others here I’ve also considered digging through the landscape editor code but experience tells me that mini-projects like these are deceptively challenging timesinks 
I also think as time goes on it may become more and more difficult to expose these landscape tools dynamically due to inter-dependencies with newer engine/rendering features so hopefully this can be achieved before it becomes too expensive (resource-wise) or technically unfeasible to implement this.
Is this feature on trello yet? I think it would get a ton of votes!