.babylon file Format - Attach Action to Scene

The global “actions” property in a .babylon file comes from the serialization of scene.actionManager (if defined).

So, you must set a value to scene.actionManager and register actions with it to populate the global “actions” property.

Just for fun, I asked ChatGPT:

The answer is the right one, except it is missing scene.actionManager = new BABYLON.ActionManager(scene); in the code example!