A mechanism that allows resources to only be used by certain nodes (slaves) in the network for finer control over where a build can run. Moreover, having such functionality might be used to limit the number of executions of a build on those machines (having N resources that can be used by a slave will also limit the number of instances that can run on that slave to N, at most).
As said in my closing comment on the linked pull requests:
I consider this feature out-of-scope for this plugin. If someone wants to revive this effort, I would propose creating an extension point for "dynamic labels" and adding this feature using a new plugin extending this one.