Hello @Craig Muckleston , Welcome to Microsoft Q&A,
I want to be able to open new windows on multiple monitors (more than 2).
Currently, ProjectionManager does not support full-screen app's window on multiple monitors, it only support to sent windows (app views) to secondary displays, and swaps main and projection views. It only limited the operation of two monitors.
but can't find a way to push the window to the desired monitor.
If you just want to push the window to the single desired monitor. you could refer Projection code sample Scenario3 that could select which monitor you want push window to.
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