Can we get layout to shift automatically when screen size is too narrow?

I'm using the default device layouts for desktop and tablet, and a custom phone layout. 

When the screen width is smaller than about 900px, numbers begin to display as pound signs (see below). In other cases, where an element is set to "entire view," the right side of a container is cut off and there's no scrollbar available to shift the view.   

Ideally, I'd like the device layout to shift automatically to phone if the screen size is narrower than 900px. I'd also prefer to use the default device layouts (without customizations) so that I don't have to tweak and maintain multiple layouts for every dashboard I create.  

I'd appreciate any advice. TIA!