Lifters are useful if you want to recycle marbles in your scene, and not just generate new ones with the generators.
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.
Vertical lifters also raise marbles. You can adjust the size, height, frequency and dump-direction of the lifters.