The index of the sheet within the published tabs. Note that hidden tabs are still
counted in the ordering, as long as they are published.
A value indicating whether the sheet is the currently active sheet.
A value indicating whether the sheet is hidden (true) or visible (false) in the UI.
Note that if the entire tab control is hidden, it does not affect the state of this flag.
This sheet may still report that it is visible even when the tabs control is hidden.