From wildfly security system configuration documentation, there is

security-properties

This element is used to specify additional properties as required by the security subsystem, properties are specified in the following format:
<security-properties>
<property name="..." value="..."/>
</security-properties>

The property element can be repeated as required for as many properties need to be defined.

Each property specified is set on the java.security.Security class.

However when I add this this configuration to standalone.xml

<subsystem xmlns="urn:jboss:domain:security:1.2">
<security-properties>
  <property name="myproperty" value="myvalue"/>
</security-properties>
</subsystem>

Then the property is not set in java.security.Security.

I digged in wildfly sources and I found this in SecuritySubsystemParser.java :

                case SECURITY_PROPERTIES:
                    reader.discardRemainder();
                    break;

It seems that this feature is not implemented.