I faced similar problem lately after the Version 7 Upgrade.
The tap and hold Recent key doesnt work anymore for the multi window.
You need to tap on the double rectangular icon (split window) for it to work
1. Open Two apps
2. Then Press the double rectangular icon (split window) on the apps right side
3. Then the 1st apps will be at the top of the window
4. 2nd apps will appear at the bottom once you tap the double rectangular icon as well.
5. The 1st Apps will remain there and you can only change the bottom apps
How to undo Split Window:
1. Close all apps, then you left with the Top 1 App in split window
2. Drag down the center split line to the bottom then No more minimize window for the 1st apps. You are back into single mode.
I hope this help.. I just figure it just now after facing problems.
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