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I did a test in our environment and the situation is the same as yours. This feature can help users improve the meeting quality when users join Teams meeting. I checked some ways but it seems there is no direct ways to reseize the windows and it look like set by design.
To get this feature more quickly, I have found a feedback in Teams UserVoice 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 problem may well be released in the future. Thanks for your understanding and support.
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