Yes, there is no way to externally set the pipeline label for the top-level pipeline invocation. The label is intended to be controlled by the pipeline developer. If the pipeline invoker can set it directly, then the pipeline developer can no longer control it.
If the requirement is to be able to search for particular pipeline run in the dashboard, it is possible to search using captured pipeline paremeters. That will allow the user to find the desired run through the dashboard. The invoker can pass any unique parameter values as required to the top-level invocation.
