Hi @Kimberly Settle ,
Based on my test, i got the same result as yours, i'm afraid that the side-by-side view is not available in New Outlook preview. It's suggested that you could turn off New Outlook button to switch to Legacy Outlook to use this feature.
To get this feature more quickly, I have found a feedback on the website dedicated to collecting feedback and you could vote for it. Many features of our current products are designed and upgraded based on customers’ feedback. With requirements like this increase, the feature may well be released in the future. Thanks for your understanding and support.
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