What is the desired functionality that you are missing?

Neither in https://docs.camunda.org/manual/develop/user-guide/ext-client/ nor in https://github.com/camunda/camunda-external-task-client-java you find concrete information on the version of the artifact to use. It is also not part of the camunda-bom.

As the client has its own versioning schema it is required to understand which client to use with which Camunda version.

Which problem are you going to solve with this functionality?

We need to explain this in the docs. Something like

You do not need to update that client if you update Camunda
1.1 requires >= Camunda 7.9
...
A bit comparable to what we do with Spring Boot (https://docs.camunda.org/manual/latest/user-guide/spring-boot-integration/version-compatibility/).