An import music button
I find that the music, or recordings on the phone or device can not be added to the que of things to be added to the video because they do not a have a “Video” of their own to them.
What it would allow is any audio files on the phone to be used, such as recordings through the voice recorder app, and/or even the Apple Music app, if the person has an iProduct.
Rush now supports Apple Files. You can access any files on your device from Rush that are saved to the Files app.