Update configuration file using script -Kubentes

I’m running mu keycloak on top Kubernetes.
In order to add a customized object, I need to update the configuration file. I have noticed that during startup there are script that updating the configuration – example of a command taken from the script :
/subsystem=datasources/data-source=KeycloakDS: write-attribute(name=user-name, value=${env.DB_USER:keycloak})

For my customized object, I need to add an additional provider (demo - the second provider) under the following structure. Can you please suggest how I should define the command?

>"<subsystem xmlns="urn:jboss:domain:keycloak-server:1.1">
>     <web-context>auth</web-context>
>     <providers>
>         <provider>classpath:${jboss.home.dir}/providers/*</provider>
>         <provider>module:demo.keycloak.organizations.demo-organizations-mapper</provider>
>     </providers>
>     <master-realm-name>master</master-realm-name>

This might be achieved via Running Custom Script on startup. Although, you’d need to learn the basics of JBoss CLI (but you will find plenty of resources on this subject on the Internet).