When a Window is maximized, the space left of the first tab is unused. We should make that space part of the click area of the first tab in that case in order to benefit from the Fitts law advantages in the edge regions of the screen. This does not apply if a toolbar icon is customized to a position left of the tab strip.

Not sure if it's the right choice. I frequently use this space to quickly unmaximize the window so it's not really unused.

FWIW, this has always been a thing, also for other versions of Windows. I think there are good reasons not to do this (comment #0, esp. from long habits of that being a place where you can get the titlebar context menu / titlebar icon to close the window or do whatever) and I don't really understand why the first tab is so particularly important compared to the other tabs. IME it almost never is, at least for me. Certainly not as important as the other things we/windows Fitts-optimize (back button, menu button, window close button). I would suggest wontfix, and/or at least not tracking as part of this win10 project.

Given it being an existing issue and not a major problem, I'd call this a P4 if we won't wontfix it.