Yes, it is. The export of AUTOSAR DEXT is available for each CDD from CANdelaStudio 8.5 SP2 on.
Find more information on the usage of AUTOSAR DEXT in Vector toolchain in this article.
Since CANdelaStudio 8.5 this functionality has been continuously extended.
As the diagnostic extract depends on the AUTOSAR version you are working with, it may be advisable to upgrade your CANdelaStudio.
Users with a license of DaVinci Configurator Pro can also use the Vector AUTOSAR XML Editor to view or edit the DEXT file. This tool is part of the DaVinci external components setup, available as a Service Pack for DaVinci Configurator Pro in the Download Center.
Note that this is an expert tool for AUTOSAR specialists.