I wrote a level design tool here to place objects, in this case collectibles, on curves using the Unity Spline package.
These are from a personal test project where I was playing with procedural noise proc gen and tiles to create an isometric survival / crafting game. All the items in the game used materials which were just scriptable objects that gave them certain properties that determine their appearance and usefulness for different tasks. I tabled this because I got busy with other things.