How can I custom resource after ray cluster start

I’m currently using an exiting Ray Cluster, and aim to launch a series of tasks when control the level of concurrency(for instance, only 3 tasks running simultaneously even with 10 tasks pending, cpus/memory available)).
I always use custom resources with self-initialed Ray Cluster before, but I find this method unsuitable as the existing Ray cluster was not initialized by me.

Any solution?