Why do we have Run External Event option grayed out when using Data Import Wizard or Rule Editor?
Data Import Wizard, Business Rules, February 2015 and newer releases
External events have been deprecated and might be permanently removed in a future release. Instead, use the Execute Object Event Handler action described in the previous row. For more information, refer to The Process Designer / Custom Process Models (CPM) functionality.
August 2015 and newer: Starting with August 2015 release, when trying to use Data Import Wizard, the option "Run External Event" is grayed out and you cannot select the option in the Service Cloud console.
February 2015: Starting with this version, the Incident Action business rule called "Execute External event." in Rule Editor is grayed out. This option was disabled in the February 2015 release.