See https://github.com/jenkins-infra/jenkins.io/pull/5018 for context: it is cumbersome to manually maintain web documentation about every system property interpreted by Jenkins. We should rather have an API allowing any code in Jenkins core or a plugin to register an experimental/unsupported "flag" which could be overridden via system property, Groovy console or perhaps even though some specialized admin GUI and CLI and/or REST command. Each flag would need to include some metadata:

• name (as used by SystemProperties)
• documentation (HTML?)
• default value
• type (boolean, nonnegative int/float, string, enum, etc.)