How do I load/unload a SubScene in ECS?

I want to load/unload subscenes but can’t figure out how. I have seen talk of RequestSceneLoaded but not exactly how to use it.

Code example below. Note that you need to do it as a ComponentSystem and not a JobComponentSystem so it will run on the main thread.

using Unity.Entities;
using Unity.Scenes;

public class ToggleSubSceneSystem : ComponentSystem {
    protected override void OnUpdate() {
        Entities.ForEach((Entity entity, SubScene scene) => {
            if (EntityManager.HasComponent<RequestSceneLoaded>(entity)) {
            } else {

        this.Enabled = false;