Lifter
Stairstep lifter
Stairstep lifters raise marbles. They can be as wide or narrow as you want, handling just one marble or many marbles at a time on each step. They can be as tall or as short as you like too.
Lifters are useful if you want to recycle marbles in your scene, and not just generate new ones with the generators.
Here is the code for a simple, one ball lifter below.
Here's a much larger lifter that can handle many balls at once. You can set the width, height, and rotation of the lifter without constraint. Here's the code for it.
Here's a screenshot of it running.
Here's what it looks like when you create one: