Can Curve Spline be used for an in game level editor.

[_Aka_]

That's great to hear. Is it possible to have generated objects be placed on nodes/points only, and have other generated objects only create between nodes?

Placing objects on the node is simple, since every node is its own GameObject, you can simply iterate through them via script and place your game objects.
For placing objects in between, you can either

• do it via script. The main methods you will need are CurvySpline.InterpolateByDistance and CurvySplineSegment.Length. Using these methods, you can find the position of points on the spline at equal distance from each other.
  
• use the Curvy Generator (using the Volume Spots module). This module offers a lot of options when it comes to placing objects on a spline.
  Here is a tutorial showing how to use the generator for that usage: https://youtu.be/jUrpY9-8xH4
  Here is the documentation of said module: https://curvyeditor.com/documentation/generator/modules/volumespots 
  

Also can nested child objects be curved?

Yes they can. In this tutorial, at the moment specified in the link, you can see that the RailBlock object has nested game objects: https://youtu.be/eP6QEn9SFoM?t=383
The scene in the tutorial is part of the package.

Hope this helped.
Have a nice day