Since "Main" and "Review" buttons are mutually exclusive, consolidate them into one toggle button. This will save one space for another button, for us who uses screens with smaller resolution.
By splitting up into separate options, it's easier to describe and understand. You may remove both buttons from the toolbar, if you prefer.
I agree with Marc, a toggle button is not very good UX.If what you want is to save space, another option is to remove the "text" under the buttons and/or remove all the buttons you never use. I personally only use 7 buttons out of the 18 I am seeing as of this writing. (well, that's because I use the context menu a lot).
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