Samsung's multi-tasking mode doesn't let you use any app that you want in its original factory settings: there is only a limited selection of apps that can be used in multi-window. That is the reason why developers had to create something that will allow Samsung Galaxy S4 owners to use any app that they want in multitasking mode.

You must have your Samsung Galaxy S4 rooted to enable all apps in Multi Window for Galaxy S4. Below is how you can enable all your apps in multitasking mode of SGS4.

How to enable Multi Window in Galaxy S4:

Required files: downloadXposedInstaller_2.1.4.apkandXposedMultiWindow.apk. The latterwill help you enable the mod.

Once you have downloaded the files, install xposed_2.1.4 apk on your phone. Follow it with installation of multi window apk.Enter the Xposed app on your device and click on install to install it.Reboot your device and then go to xposed app. Check the multi window module.Reboot your Galaxy S4 again.Simply now drag the apps that you want in the Multi Window panel on the left. Then drag any two apps on the screen to run them simultaneously.

That is done! You can now enjoy any of the apps you want in the multi window mode of Samsung Galaxy S4.