Plugins versions can be centralized in the settings script. Unfortunately Kotlin settings script cannot read Gradle properties, yet, see
https://github.com/gradle/kotlin-dsl/issues/635. In the meantime you could work around the limitation by either put the kotlin version in a file and read it both in settings/project scripts, or, in an object defined in buildSrc, or using the same trick as
https://github.com/gradle/kotlin-dsl/pull/653, or use a Groovy settings script.