In order to accomplish using SAML Authentication via Vidyo Desktop Window (Not in External Browser), a registry or plist entry needs to be added.

On windows set registry: 

[HKEY_CURRENT_USER\Software\Vidyo\VidyoDesktop3\external]
"AuthenticationMethod"="SAML"
"SAMLAuthenticationURL"="https://saml1.support.com"

 On Mac set plist:

*Download xCode from the AppStore*

Under ~/Library/Preferences/ (click on Go – hold option key – while holding click on the new line Library, after that open the preference folder)

Open the following plist files with xCode.

In plist - com.vidyo.VidyoDesktop3.plist - the following keys should be updated 

external.AuthenticationMethod = SAML (empty for portal/LDAP)

external.SAMLAuthenticationUrl = <tenetURL enabled with SAML>

Example:

external.AuthenticationMethod = SAML

external.SAMLAuthenticationUrl = https://saml1.support.com

Please remember to quit VD before and refresh plist cache after editing (in terminal run the following command - defaults read ~/Library/Preferences/com.vidyo.VidyoDesktop3.plist)