You can still use Export Field Contents, you just need more than one and an IF block that determines which panel of the slide control is the front panel at the time the script executes. Or, if you use a button on the slide control panel to do the export, you can include a script parameter that tells the script which to use for the export.
Use the Name box in the Inspector to give each panel of your tab control an objectname.
Use the IsFrontPanel attribute of GetLayoutObjectAttribute to test to see which panel is currently the front.
Alternatively, you can use the OnPanelSwitch trigger with Get ( TriggerTargetPanel ) to set a global variable to a value that can be checked to see which panel is currently the front panel.