Contrary to comment #5, Microsoft Edge on Windows hides the vertical tabs on Windows on fullscreen, as of version 132.0.2957.140 on the stable channel.
Bug 1927457 Comment 14 Edit History
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Contrary to comment #5, Microsoft Edge on Windows hides the vertical tabs on Windows on fullscreen, as of version 132.0.2957.140 on the stable channel. (Which is already mentioned in comment #9 but just reconfirming)