Hello,
This is an observation of an unexpected behavior...
Consider the case using a Tabs component with a vertical Sidebar. The Tabs is set with OverflowMode = Scrollable and with multiple Tab Items defined.
With the Sidebar IsOpen = false, resize the application window so all tabs use the (almost) full width of the Tabs component (no scroll arrows in the Tabs header section). Now set Sidebar IsOpen = true. The right-most tab is now not completely visible however, there are no scroll arrows in the Tabs header.
Flip the situation and, with IsOpen=true, size the application windows to the point where the Tab header scroll arrows are just displayed. Now set IsOpen=false. All the tabs fit in the Tabs component but the scroll arrows are still displayed.
Peter