I am looking at the Java code, and I see the following in the file saml20\implementation\artifactHandler.java:
* JVDH20170117: The module is using the username inconsistently. Introducing a setting to allow the user to configure if names are case-sensitive.
* To remain backwards compatibility we can't just create that setting becuase depending on the option they may or may not be case-sensitive.
* If the constant is specified we should follow that rule, otherwise keep the current behavior.
* We should get rid of this special case with the Mx7 release and always use the constant defaulting to true.
if( Boolean.TRUE.equals( Constants._getInstance().PRINCIPAL_TO_LOWERCASE ) )
userPrincipal = userPrincipal.toLowerCase();
The constant it is looking for is PRINCIPAL_TO_LOWERCASE, which is set by the value "sso.principalvalue.tolowercase" set in the file <projectHome>/resources/SAMLconfig.properties.
So it isn't something that is set in the Modeler or in the front-end configuration, but rather in the accompaning resource .properties file.