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I believe you are asking about the Mission Control feature?
Get a bird’s-eye view of all the open windows and apps on your Mac. Just swipe up with three fingers on your trackpad or click the Mission Control icon in the Dock, and your desktop zooms out to Mission Control.
I am not asking about the mission control feature.
I would like to view e.g. 2 app's on the SAME screen, so that E.G. I can enter details of an AMEX bill into my accounting softwaren by simply glancing at the ONE screen vs the need to swipe back and forth BETWEEN screens. The key I am looking for would instantly place both apps on the one screen and SIZE them equally to fill all the available screen space so they are as large as possible sharing the scren.