is something that cannot be done currently. would be a cool to put in. Post in the feedback section of the forums for a request and accompanying features you’d like to see and I’ll see if I can get a request in for that soon.
For the landscape spline, when you create the corners you can smooth them out more by selecting a segment > hold ctrl > click and it’ll pop another point between the two segments. Not sure if you were aware of that one or not.