Side by side two paned editor in addition to what happens today with top and bottom

With the increasing use of multiple monitors at customer sites, it would be nice to be able to have the two paned editor have the current top and bottom source vs wysiwyg (almost) view, with a toggle button that allows these to be side by side instead of top to bottom.

Source Code
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Rendering

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Source + Rendering
Code +
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It would be nice to toggle/flip Source Code and Rendering via a selectable button. ie

These can be flipped
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Rendering + code
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