Specifies the name of the sidebar that is connected to the RibbonFormattingTab's TXITEM_StyleName's Change Styles drop down item. The property value is String.Empty, if there is no sidebar connected.
Clicking the TXITEM_StyleName's Change Styles drop down item displays or hides the connected sidebar. On clicking the item to show the sidebar, its content layout is set to SidebarContentLayout.Styles.