Go to
%LOCALAPPDATA%\Microsoft\Windows\Shell\
Edit LayoutModification.xml (remove the inner taskbar items)
<CustomTaskbarLayoutCollection PinListPlacement="Replace">
<defaultlayout:TaskbarLayout>
<taskbar:TaskbarPinList>
<taskbar:DesktopApp DesktopApplicationLinkPath="%APPDATA%\Microsoft\Windows\Start Menu\Programs\System Tools\File Explorer.lnk" />
<taskbar:DesktopApp DesktopApplicationLinkPath="%ALLUSERSPROFILE%\Microsoft\Windows\Start Menu\Programs\Outlook.lnk" />
</taskbar:TaskbarPinList>
</defaultlayout:TaskbarLayout>
</CustomTaskbarLayoutCollection>