The Security subsystem in Configuration => Subsystems should contain also subtitle "Elytron" so that it's clear what can be configured there and it can be found by typing (Ctrl+F).

There is a similar case: Web/Undertow.

The right place is probably https://github.com/hal/console/blob/main/core/src/main/java/org/jboss/hal/core/subsystem/Subsystems.java#L77

The similar Undertow case is at https://github.com/hal/console/blob/main/core/src/main/java/org/jboss/hal/core/subsystem/Subsystems.java#L200