VDA Diagnostic data will be created by Call Home (Telemetry Service) in the Customer Environment of the XenDesktop/XenApp 7.6 FP3 new release.
Since Nov 21, this data bundle has been supported in CIS:
Customers can use telemetry service to create a bundle that can either be manually uploaded or directly uploaded by the telemetry service to CIS. When CIS receive this bundle, CIS can recognize this bundle, and decode the bundle to meaningful package which can be read by support. CIS will save this decoded bundle to Vault folder.
In the not-too-distant future, CIS will give more support for this bundle.
More information about XA/XD Callhome, please refer to https://www.citrix.com/blogs/2015/11/24/citrix-call-home-feature-in-the-xenapp-and-xendesktop-7-6-fp3/