This is a tremendous idea, I have asked for this in many Betas. It has yet to be implemented. My solution for this want are 2 different apps to give me stackable folders. called Widget Folders and Glass Widgets on the bottom of my homescreen I have horizontal folders that I scroll through instead of having a dock using Glass Widgets. On my 2nd screen on the bottom I use Folder Widget which are a vertical scroll. I then put a cover stack to hide them when not using. 
