That is an interesting page you linked to.
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Show changes is the Excel version of Word Track Changes. It would have been nice if MS had used the same name for the feature. Definitely would be useful in an online "co-authoring" scenario, such as online co-authoring. I've always liked the idea of track changes, but never could get comfortable using the Word version.
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Targeted release builds is one of the "channels" that the corporate Office Admin can control. But I thought it was limited to the installed versions of Office. The online version is run dynamically on the web. There is no mention of channels in the About dialog in Excel Online. I could be wrong, but I don't see how Office desktop settings could control an online version. I suppose there could be something in the user profile that controls what is displayed in the browser. But I wish there was an indication.
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For what ever it is worth, I don't see the new feature in my Excel Online.
100% Agree, I was thinking I cannot see desktop controlling web but maybe it will. I'd love to know how to get it on the web!