Once you enable Multiple Arm mode for your measurement routine, any dialog boxes or message boxes that are related to a specific arm contain an "Arm 1" or "Arm 2" identifier in their captions, like these Execution dialog boxes:
Dialog and message boxes that are affected include:
Execution dialog box (File | Execute)
Probe Changer dialog box (Edit | Preferences | Probe Changer)
Info messages
Warning messages
Error messages