If you bring up one of your nodes (by clicking on the node name in the status or browsing to it via "Manage Nodes") you get a list of labels on that page.

If you click on a label it lets you know what projects are using that label. However, any jobs that use the label as part of a logical expression (i.e. Label1 && ( Label2 || Label3) don't appear on the list. This means that as far as I can tell there is no way to track down all of the jobs that are currently using a particular label unless they are using it individually.

This makes it really hard to manage label usage and to maintain labels if you need to update some... you have to wait for the job to "fail" because it can no longer find the correct label as a means to track them down.

My apologies in advance if this has already been addressed somewhere. I looked around for quite a while and didn't find anything.