The desired behavior can be achieved by modifying the Window source code. You can take a look at the following methods where the Window position and dimensions are set during maximization and browser window resize.
In maximize() the Window top / left position is set to zero / zero, which is the top-left browser viewport point. In _onDocumentResize the Window widht and height are set to be equal to the browser viewport width and height. You can change these values.
There is a way to achieve the same result without modifying the source, but this will involve changing the Window's position and size after the widget have already done this, which may result in visible flickering.
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