How do we access objects from other loaded scenes?

We want to load an additional (but separate) scene into an html element.
I can achieve this via code:

var additionalApp = new v3d.App(container, null, preloader);

additionalApp.loadScene('AdditionalScene.glb', function() {        
    additionalApp.run();
});

The new app shows up fine and it gets added to the apps list.
Unfortunately, none of the puzzles work with this additional app.
For example, I want to use the “when clicked object” puzzle, but I can’t select objects from the additional scene.