Node Mirroring (understanding the application for Kubernetes)

### Describe your use-case which is not covered by existing documentation.

I am looking for how to apply this to limit the amount of concurrent agents that are created on-demand by Jenkins SaaS w/ Kubernetes. It seems like I can possibly combine quantity and label to do so? However, the documentation does not confirm this use case. In fact, node mirroring seems like it is supposed to work for static agents.

Please forgive any ignorance, and any response would help me.

Thank you for your good work.

### Reference any relevant documentation, other materials or issues/pull requests that can be used for inspiration.

_No response_

### Are you interested in contributing to the documentation?

_No response_