Specifies the name of a field that will contain the index of the selected tab. This is similar to the selected_tab_index property Indeed you can specify a field name for the selected_tab_index property and its value will control the index of the tab that is initially selected. But using this property instead has the additional effect of updating the field with the index of the currently selected tab. If this field is posted back to the webroutine, then your program code can know which tab was last shown. You may, for example, wish to save this information and use it the next time the webroutine is loaded for the same user to show them the same tab they displayed on their previous visit.
The name of a field present in the web-map for your WebRoutine. (Usually you will specify a numeric field that is large enough to contain the highest tab number.) The field name should be specified in single quotes. Click the drop-down arrow next to this property to choose from a list of available field names.