I'm deploying Jenkins instances with Jenkins Configuration as Code but I lacked a lot of information and especially about Maven configuration in Tool configuration page (i.e. <JENKINS_URL>/configureTools) .

Using JCasC slides, source code and error logs, I found that I can use (e.g. using Config Files):

tool:
  maven:
    globalSettingsProvider:
      mvn:
        settingsConfigId: maven-default-settings