How to Configure Shortcut Keys for Windows 8 Apps

Use Autohotkey. The scripting language is non standard and can be difficult to learn, but if all you're wanting to do is reliably launch programs, its simple. Plus you can base shortcuts off the Windows key! Use following sample script and modify it to your needs. (Lines starting with ; are comments.)

;win + alt + e ... unload ipod
#!E::
   run d:\Downloads\Apps\deveject\eject ipod.bat
   return

;win + w ... launch winamp
#w::
    run c:\program files (x86)\winamp\winamp.exe
    return

;win + a ... launch AS400
#a::
    run C:\Program Files (x86)\IBM\Client Access\Emulator\Private\1.ws
    return

;win + Shift a ... launch AS400 Printer
#+a::
    run C:\Program Files (x86)\IBM\Client Access\Emulator\Private\3.ws
    return

;win + ctrl + Shift a ... launch 2nd AS400 
#^+a::
    run C:\Program Files (x86)\IBM\Client Access\Emulator\Private\2.ws
    return

Save this as a .ahk file on your desktop, install autohotkey and run it.

Every time you press any key combination, AutoHotkey will scan this script. If it matches any of the key combinations that preceed a ::, it will execute the next command. If the return statement is missing, the AHK will continue to scan the script for matches after executing your statement. The key combinations are described below.

# = Windows Key
+ = Shift
^ = Control
! = Alt

You can use these in any combination with the letters of your keyboard. One combination I find extremely useful is as follows.

; ALT Backtick ... ctrl f4
!`::
    Loop, parse, RcvCtrlW, `,
    {
     IfWinActive %A_LoopField%
     {
        sendinput ^w
        Return
     }
    }
    sendinput ^{f4}
    return

; win Backtick ... alt f4
#`::
   sendinput !{f4}
   return   

This is Alt + ` and Win + `. When this script is running and I press alt + `, the script sends ctrl + F4. Win + ` becomes alt + F4.

Autohotkey is basically its own programming language. I have scripts set up that simulate "Rocker Gestures" system wide. I have GMail like shortcuts for my email. If you spend the time to learn some of its tricks, you can get nuts with it. Lifehacker has a whole bunch of useful scripts for Autohotkey. Have Fun!

Short answer! There is no shortcut to do it.

May be someone do it with autohotkey script when they will give a support to Modern UI apps.

Edit: According to your last lines for snap shortcut there is

Win+. for snap current Modern UI to right side

Win+Shift+. for snap current Modern UI to left side