@gphillips58
As per the blogs here[0][1], it depends on what you want to debug :
to debug the Host Controller (that means the server that manages the domain) use the domain.conf file or set the environment variable PROCESS_CONTROLLER_JAVA_OPTS
PROCESS_CONTROLLER_JAVA_OPTS="$PROCESS_CONTROLLER_JAVA_OPTS -agentlib:jdwp=transport=dt_socket,address=8788,server=y,suspend=n"
to debug a server instance of your domain you have to pass jvm args in your host.xml, for example to debug server-one. I assume this must be the case, so more details provided in the blogs.
[0] - https://developer.jboss.org/thread/230399
[1] - https://stackoverflow.com/questions/26927082/wildfly-domain-mode-debug