Here is how to do it:
1. Using SQlite editor go to settings storage and open it.
2. You will see a file settings.db
3. Open it and go to system.
4. Under system scroll down to open_multi_window_view
5. Change the value from 0 to 1.
6. Save and reboot.
Hi all first post on XDA. I discovered a small tweak that would would automatically open an app in Multiwindow mode. Say you are on Google search results and one of the results is on YouTube or play store, clicking that result would automatically open the app in Multiwindow mode instead of a new window. Clicking the whatsapp icon under any of your contacts will also open whatsapp in multiwindow mode.