You can add as many files as you like; each one appears in the XRef Files window.
You can affect the display of the XRef scene, making it visible or not, or making objects in the referenced scene appear as bounding boxes. You can ignore the file's lights, cameras, shapes, helpers, or animation. You can control when the file updates, either automatically or on demand. You can have the file enabled or disabled, or you can merge it, severing the XRef relationship and inserting the scene into your current file. You can bind the scene to a Parent object to reposition or animate the XRef scene.