Run these commands, which will restart the desktop window manager service. (howtogeek.com)
Locate the Desktop Window Manager Session Manager service and change its Startup type to Disabled. (thewindowsclub.com)
Although we weren't able to preview this mode ahead of today's announcement, it appears to be almost identical to the Mate 10's implementation, which has its own basic window manager for resizing Android apps. (androidcentral.com)