Ability to add multiple code splits in Design Mode

As a user, I use edit mode only for the ability to split my code window and view multiple files side by side.  If I could do this in Design mode I would have little need for edit mode.  

As a user I would like to be able to add additional code panels/split the code panel in Design mode and then be able to dynamically select and lock what page is displayed in the 2D View as well as Live Preview.