Principal username (usually email): {%PrincipalUserName%}

Displayed name: {%DisplayedUserName%}

Detailed Description
Regular session:

Role session:
[07/févr./2020 17:09:53] PrincipalUserName is LeeG@M365x831182.OnMicrosoft.com|~#~|TEST FOR LOGS
[07/févr./2020 17:09:53] PrincipalUserEmail is LeeG@M365x831182.OnMicrosoft.com
Example Script
<Echo Value="{%PrincipalUserName%}"/>
<Echo Value="{%DisplayedUserName%}"/>
XML