A bit hard to tell from your question and a huge code snippet.
In general: By making the method public static so it can be called from anywhere (assuming the wrapping type is visible of course) ... might need to refactor a bit to not rely on any instance fields but rather take parameters (using ref/out where required)
I didn't count the lines but I will just assume you are referring to CreateNewGrassObject (it's the only non-drawer related thing you included in your question)
So I would convert this to
public static GrassComputeScript CreateNewGrassObject()
{
var grassObject = new GameObject();
grassObject.name = "Grass System - Holder";
var grassCompute = grassObject.AddComponent<GrassComputeScript>();
// Why is this not simply done in the GrassComputeScript by default on field declaration?
grassCompute.SetGrassPaintedDataList = new List<GrassData>();
return grassCompute;
}
all other local values are available then as well anyway via e.g.
var newGrass = GrassPainterWindow.CreateNewGrassObject();
var gameObject = newGrass.gameObject;
var grassData = newGrass.SetGrassPaintedDataList;
Since it contains no editor specific code, you might even consider to move this out into a helper class like
public static class GrassTools
{
public static GrassComputeScript CreateNewGrassObject()
{
...
}
}
so it could be available even in a build.
